Physio-molecular traits of contrasting bread wheat genotypes associated with 15N influx exhibiting homeolog expression bias in nitrate transporter genes under different external nitrate concentrations.

MAIN CONCLUSION: The high affinity nitrate transport system is a potential target for improving nitrogen use efficiency of bread wheat growing either under optimal or limiting nitrate concentration. Nitrate uptake is one of the most important traits to take into account to improve nitrogen use efficiency in wheat (Triticum aestivum L.). In this study, we aimed to gain an insight into the regulation of NO3- -uptake and translocation systems in two contrasting wheat genotypes [K9107(K9) vs. Choti Lerma (CL)]. Different conditions, such as NO3--uptake rates, soil-types, N-free solid external media, and external NO3- levels at the seedling stage, were considered. We also studied the contribution of homeolog expression of five genes encoding two nitrate transporters in the root tissue, along with their overall transcript expression levels relative to specific external nitrate availability. We observed that K9107 had a higher 15N influx than Choti Lerma under both limiting as well as optimum external N conditions in vermiculite-perlite (i.e., N-free solid) medium, with the improved translocation efficiency in Choti Lerma. However, in different soil types, different levels of 15N-enrichment in both the genotypes were found. Our results also demonstrated that the partitioning of dry matter in root and shoot was different under these growing conditions. Moreover, K9107 showed significantly higher relative expression of TaNRT2.1 at the lowest and TaNPF6.1 and TaNPF6.2 at the highest external nitrate concentrations. We also observed genotype-specific and nitrate starvation-dependent homeolog expression bias in all five nitrate transporter genes. Our data suggest that K9107 had a higher NO3- influx capacity, involving different nitrate transporters, than Choti Lerma at the seedling stage.

Comparative transcriptome profiling of Polianthes tuberosa during a compatible interaction with root-knot nematode Meloidogyne incognita.

BACKGROUND: The root-knot nematode (RKN; Meloidogyne spp.) is the most destructive plant parasitic nematode known to date. RKN infections, especially those caused by Meloidogyne incognita, are one of the most serious diseases of tuberose. METHODS AND RESULTS: To investigate the molecular mechanism in the host-pathogen interactions, the Illumina sequencing platform was employed to generate comparative transcriptome profiles of uninfected and Meloidogyne incognita-infected tuberose plants, during early, mid, and late infection stage. A total of 7.5 GB (49 million reads) and 9.3 GB (61 million reads) of high-quality data was generated for the control and infected samples, respectively. These reads were combined and assembled using the Trinity assembly program which clustered them into 1,25,060 unigenes. A total of 85,360 validated CDS were obtained from the combined transcriptome whereas 6,795 CDS and 7,778 CDS were found in the data for the control and infected samples, respectively. Gene ontology terms were assigned to 958 and 1,310 CDSs from the control and infected data, respectively. The KAAS pathway analysis revealed that 1,248 CDS in the control sample and 1,482 CDS in the infected sample were enriched with KEGG pathways. The major proportions of CDS were annotated for carbohydrate metabolism, signal transduction and translation related pathways in control and infected samples. Of the 8,289 CDS commonly expressed between the control and infected plants, 256 were significantly upregulated and 129 were significantly downregulated in the infected plants. CONCLUSIONS: Collectively, our results provide a comprehensive gene expression changes in tuberose during its association with RKNs and point to candidate genes that are involved in nematode stress signaling for further investigation. This is the first report addressing genes associated with M. incognita-tuberose interaction and the results have important implications for further characterization of RKN resistance genes in tuberose.

Raffinose accumulation and preferential allocation of carbon (14 C) to developing leaves impart salinity tolerance in sugar beet.

Sugar beet is a salt-tolerant crop that can be explored for crop production in degraded saline soils. Seeds of multigerm genotypes LKC-2006 (susceptible) and LKC-HB (tolerant) were grown in 150 mM NaCl, from germination to 60 days after sowing, to decipher the mechanism of salinity tolerance at the vegetative stage. The biomass of the root and leaf were maintained in the tolerant genotype, LKC-HB, under saline conditions. Na+ /K+ ratios were similar in roots and leaves of LKC-HB, with lower values under salinity compared to LKC 2006. Infrared temperatures were 0.96°C lower in LKC-HB than in LKC-2006, which helped regulate the leaf water status under stressed conditions. Pulse-chase experiment showed that 14 C photosynthate was preferentially allocated towards the development of new leaves in the tolerant genotype. The sugar profile of leaves and roots showed accumulation of raffinose in leaves of LKC-HB, indicating a plausible role in imparting salinity tolerance by serving as an osmolyte or scavenger. The molecular analysis of the genes responsible for raffinose synthesis revealed an 18-fold increase in the expression of BvRS2 in the tolerant genotype, suggesting its involvement in raffinose synthesis. Our study accentuated that raffinose accumulation in leaves is vital for inducing salinity tolerance and maintenance of shoot dry weight in sugar beet.

Investigation on comparative transcriptome profiling of resistant and susceptible non-CMS maize genotypes during Bipolaris maydis race O infection.

Maydis leaf blight is a significant disease of maize caused by Bipolaris maydis race T, O and C. Molecular mechanisms regulating defense responses in non-CMS maize towards race O fungus are not fully known. In the present investigation, comparative transcriptome profiling was conducted on a highly resistant maize genotype SC-7-2-1-2-6-1 against a standard susceptible variety CM 119 at 48 h post inoculation (h PI) along with non-infected control. mRNA sequencing generated 38.4 Gb data, where 9349602 reads were mapped uniquely in SC-7, whereas 2714725 reads were mapped uniquely in CM-119. In inoculated SC-7, the total number of differentially expressed genes (DEGs) against control was 1413, where 1011 were up-regulated, and 402 were down-regulated. In susceptible inoculated genotype CM 119, the number of DEGs against control was 2902, where 1703 were up-, and 1199 were down-regulated. DEGs between inoculated resistant and susceptible genotypes were 10745, where 5343 were up-, and 5402 were down-regulated. The RNA-seq data were validated using RT-qPCR. The key findings are that SC-7 poses a robust plant signaling system mainly induced by oxidation-reduction process and calcium-mediated signaling. It regulates its fitness-related genes efficiently, viz., aldolase 2 gene, isopropanoid, phyto hormones, P450 cytochrome, amino acid synthesis, nitrogen assimilation genes etc. These findings showed more transcriptional changes in the SC-7 genotype, which contains many defence-related genes. They can be explored in future crop development programmes to combat multiple maize diseases. The current finding provides information to elucidate molecular and cellular processes occurring in maize during B. maydis race O infection.

Starch and storage protein dynamics in the developing and matured grains of durum wheat and diploid progenitor species.

Durum wheat, less immunogenically intolerant than bread wheat, originates from diploid progenitors known for nutritional quality and stress tolerance. Present study involves the analysis of major grain parameters, viz. size, weight, sugar, starch, and protein content of Triticum durum (AABB genome) and its diploid progenitors, Triticum monococcum (AA genome) and Aegilops speltoides (BB genome). Samples were collected during 2-5 weeks after anthesis (WAA), and at maturity. The investigation revealed that T. durum displayed the maximum grain size and weight. Expression analysis of Grain Weight 2 (GW2) and Glutamine Synthase (GS2), negative and positive regulators of grain weight and size, respectively, revealed higher GW2 expression in Ae. speltoides and higher GS2 expression in T. durum. Further we explored total starch, sugar and protein content, observing higher levels of starch and sugar in durum wheat while AA genome species exhibited higher protein content dominated by the fractions of albumin/globulin. HPLC profiling revealed unique sub-fractions in all three genome species. Additionally, a comparative transcriptome analysis also corroborated with the starch and protein content in the grains. This study provides valuable insights into the genetic and biochemical distinctions among durum wheat and its diploid progenitors, offering a foundation for their nutritional composition.

Studies on pollen micro-morphology, pollen storage methods, and cross-compatibility among grape (Vitis spp.) genotypes.

The knowledge of pollen morphology, suitable storage condition, and species compatibility is vital for a successful grapevine improvement programme. Ten grape genotypes from three different species, viz., Vitis vinifera L., Vitis parviflora Roxb., and Vitis champini Planc., were studied for their pollen structure and pollen storage with the objective of determining their utilization in grape rootstock improvement programs. Pollen morphology was examined through the use of a scanning electron microscope (SEM). The viability of the pollen was assessed using 2,3,5-triphenyltetrazolium chloride (TTC). In vitro pollen germination was investigated using the semi-solid medium with 10 % sucrose, 100 mg/L boric acid, and 300 mg/L calcium nitrate. The results revealed variations in pollen micro-morphology in 10 genotypes, with distinct pollen dimensions, shapes, and exine ornamentation. However, species-wise, no clear difference was found for these parameters. Pollen of V. parviflora Roxb. and Dogridge was acolporated and did not germinate. The remaining eight genotypes exhibited tricolporated pollen and showed satisfactory in vitro pollen germination. Storage temperature and duration interactions showed that, at room temperature, pollen of most of the grape genotypes can be stored for up to 1 day only with an acceptable pollen germination rate (>30 %). However, storage for up to 7 days was successfully achieved at 4 °C, except for 'Pearl of Csaba'. The most effective storage conditions were found to be at -20 °C and -196 °C (in liquid N2), enabling pollen storage for a period of up to 30 days, and can be used for pollination to overcome the challenge of asynchronous flowering. Four interspecific combinations were studied for their compatibility, among which V. parviflora Roxb. × V. vinifera L. (Pusa Navrang) and V. parviflora Roxb. × V. champini Planc. (Salt Creek) showed high cross-compatibility, offering their potential use for grape rootstock breeding. However, V. parviflora Roxb. × V. vinifera L. (Male Hybrid) recorded the lowest compatibility index among studied crosses. In the case of self-pollinated flowers from V. parviflora Roxb. and V. parviflora Roxb. × V. champini Planc. (Dogridge), pollen failed to germinate on the stigma due to male sterility caused by acolporated pollen. As a result, the flowers of these genotypes functioned as females, which means they are ideal female parents for grape breeding without the need for the tedious process of emasculation.

Exploring protein structural adaptations and polyphenol interactions: Influences on digestibility in pigeon pea dal and whole grains under heat and germination conditions.

Pigeon pea, a protein-rich legume with low protein digestibility (PD) due to its high polyphenol content and other antinutritional factors (ANFs). Consequently, processing methods are crucial to improve PD. We investigated the effects of thermal treatments (cooking, hydrothermal, autoclaving, infrared rays) treatments and germination on modulation of PD, its properties and association with ANFs in two distinct genotypes based on polyphenol content: high (Pusa Arhar 2018-4) and low (ICP-1452). Treatments improved in vitro PD and essential amino acid content, with autoclaving showing significantly higher PD (ICP-1452: 90.4%, Pusa-Arhar 2018-4: 84.32%) ascribed to disruption of tight protein matrices. Significant increase in ß-turn, reduction in protein: starch, protein: polyphenol interactions as well as breakdown of storage proteins revealed by the analysis of protein structural properties. This study suggests thermal treatments, particularly autoclaving, can enhance pigeon pea protein's nutritional quality for its utilization as a new ingredient in development of healthy foods.

Nitrogen uptake and remobilization from pre- and post-anthesis stages contribute towards grain yield and grain protein concentration in wheat grown in limited nitrogen conditions.

Background: In wheat, nitrogen (N) remobilization from vegetative tissues to developing grains largely depends on genetic and environmental factors. The evaluation of genetic potential of crops under limited resource inputs such as limited N supply would provide an opportunity to identify N-efficient lines with improved N utilisation efficiency and yield potential. We assessed the genetic variation in wheat recombinant inbred lines (RILs) for uptake, partitioning, and remobilization of N towards grain, its association with grain protein concentration (GPC) and grain yield. Methods: We used the nested association mapping (NAM) population (195 lines) derived by crossing Paragon (P) with CIMMYT core germplasm (P × Cim), Baj (P × Baj), Watkins (P × Wat), and Wyalkatchem (P × Wya). These lines were evaluated in the field for two seasons under limited N supply. The plant sampling was done at anthesis and physiological maturity stages. Various physiological traits were recorded and total N uptake and other N related indices were calculated. The grain protein deviation (GPD) was calculated from the regression of grain yield on GPC. These lines were grouped into different clusters by hierarchical cluster analysis based on grain yield and N-remobilization efficiency (NRE). Results: The genetic variation in accumulation of biomass at both pre- and post-anthesis stages were correlated with grain-yield. The NRE significantly correlated with aboveground N uptake at anthesis (AGNa) and grain yield but negatively associated with AGN at post-anthesis (AGNpa) suggesting higher N uptake till anthesis favours high N remobilization during grain filling. Hierarchical cluster analysis of these RILs based on NRE and yield resulted in four clusters, efficient (31), moderately efficient (59), moderately inefficient (58), and inefficient (47). In the N-efficient lines, AGNa contributed to 77% of total N accumulated in grains, while it was 63% in N-inefficient lines. Several N-efficient lines also exhibited positive grain protein deviation (GPD), combining high grain yield and GPC. Among crosses, the P × Cim were superior and N-efficient, while P × Wya responded poorly to low N input. Conclusions: We propose that traits favouring pre- or post-anthesis biomass accumulation and pre-anthesis N uptake may be targeted for breeding to improve grain-yield under limited N. The lines with positive GPD, a first report of genotype-dependent GPD associated with both AGNpa and AGNa in wheat, may be used as varieties or genetic resources to improve grain yield with high GPC for sustainable development under limited N conditions. Supplementary Information: The online version contains supplementary material available at 10.1186/s43170-023-00153-7.

Comparative Transcriptome Analysis of Fungal Pathogen Bipolaris maydis to Understand Pathogenicity Behavior on Resistant and Susceptible Non-CMS Maize Genotypes.

Bipolaris maydis is pathogen of maize which causes maydis leaf blight disease. In India major losses occur due to the B. maydis race "O" pathogen, whereas in other parts of the world, major losses are due to the race "T" pathogen. In the present study, we conducted an in planta transcriptomics study of the B. maydis race "O" pathogen after infection on non-CMS maize resistant and susceptible genotypes by mRNA sequencing to understand the molecular basis of pathogenicity for better management of the pathogen. Approximately 23.4 GB of mRNA-seq data of B. maydis were obtained from both resistant and susceptible maize backgrounds for fungus. Differentially expressed genes (DEGs) analysis of B. maydis in two different genetic backgrounds suggested that the majority of highly DEGs were associated with mitochondrial, cell wall and chitin synthesis, sugar metabolism, peroxidase activity, mitogen-activated protein kinase (MAPK) activity, and shikimate dehydrogenase. KEGG analysis showed that the biosynthetic pathways for secondary metabolism, antibiotics, and carbon metabolism of fungus were highly enriched, respectively, in susceptible backgrounds during infection. Previous studies in other host pathogen systems suggest that these genes play a vital role in causing disease in their host plants. Our study is probably the first transcriptome study of the B. maydis race "O" pathogen and provides in-depth insight of pathogenicity on the host.

Overexpression of a DUF740 family gene (LOC_Os04g59420) imparts enhanced climate resilience through multiple stress tolerance in rice.

Functional characterization of stress-responsive genes through the analysis of transgenic plants is a standard approach to comprehend their role in climate resilience and subsequently exploit them for sustainable crop improvement. In this study, we investigated the function of LOC_Os04g59420, a gene of DUF740 family (OsSRDP-Oryza sativa Stress Responsive DUF740 Protein) from rice, which showed upregulation in response to abiotic stress in the available global expression data, but is yet to be functionally characterized. Transgenic plants of the rice OsSRDP gene, driven by a stress-inducible promoter AtRd29A, were developed in the background of cv. Pusa Sugandh 2 (PS2) and their transgene integration and copy number were confirmed by molecular analysis. The three independent homozygous transgenic plants (AtRd29A::OsSRDP rice transformants) showed better resilience to drought, salinity, and cold stresses, but not heat stress, as compared to the non-transformed PS2, which corresponded with their respective relative transcript abundance for OsSRDP. Transgenic plants maintained higher RWC, photosynthetic pigments, and proline accumulation under drought and salinity stresses. Furthermore, they exhibited less accumulation of reactive oxygen species (ROS) than PS2 under drought stress, as seen from the transcript abundance studies of the ROS genes. Under cold stress, OsSRDP transgenic lines illustrated minimal cell membrane injury compared to PS2. Additionally, the transgenic plants showed resistance to a virulent strain of rice blast fungus, Magnaporthe oryzae (M. oryzae). The promoter analysis of the gene in N22 and PS2 revealed the presence of multiple abiotic and biotic stress-specific motif elements supporting our observation on multiple stress tolerance. Based on bioinformatics studies, we identified four potential candidate interaction partners for LOC_Os04g59420, of which two genes (LOC_Os05g09640 and LOC_Os06g50370) showed co-expression under biotic and drought stress along with OsSRDP. Altogether, our findings established that stress-inducible expression of OsSRDP can significantly enhance tolerance to multiple abiotic stresses and a biotic stress.

Genome-wide association studies reveal putative QTLs for physiological traits under contrasting phosphorous conditions in wheat (Triticum aestivum L.).

A Genome-wide association (GWAS) study was conducted for phosphorous (P)-use responsive physiological traits in bread wheat at the seedling stage under contrasting P regimes. A panel of 158 diverse advanced breeding lines and released varieties, and a set of 10,800 filtered single nucleotide polymorphism (SNP) markers were used to study marker-trait associations over the eight shoot traits. Principle component analysis separated the two environments (P regimes) because of the differential response of the traits indicating the essentiality of the separate breeding programmes for each environment. Significant variations for genotypic, environmental, and genotype × environment (GEI) effects were observed for all the traits in the combined analysis of variance with moderately high broad sense heritability traits (0.50-0.73). With the different algorithms of association mapping viz., BLINK, FarmCPU, and MLM, 38 unique QTLs under non-limiting P (NLP) and 45 QTLs for limiting P (LP) conditions for various shoot traits were identified. Some of these QTLs were captured by all three algorithms. Interestingly, a Q.iari.dt.sdw.1 on chromosome 1D was found to explain the significant variations in three important physiological traits under non-limiting phosphorus (NLP) conditions. We identified the putative candidate genes for QTLs namely Q.iari.dt.chl.1, Q.iari.dt.sdw.16, Q.iari.dt.sdw.9 and Q.iari.dt.tpc.1 which are potentially involved in the mechanism regulating phosphorus use efficiency through improved P absorption due to improved root architectural traits and better mobilization such as sulfotransferase involved in postembryonic root development, WALLS ARE THIN1 (WAT1), a plant-specific protein that facilitates auxin export; lectin receptor-like kinase essentially involved in plant development, stress response during germination and lateral root development and F-box component of the SKP-Cullin-F box E3 ubiquitin ligase complex and strigolactone signal perception. Expression profiling of putative genes located in identified genomic regions against the wheat expression atlas revealed their significance based on the expression of these genes for stress response and growth development processes in wheat. Our results thus provide an important insight into understanding the genetic basis for improving PUE under phosphorus stress conditions and can shape the future breeding programme by developing and integrating molecular markers for these difficult-to-score important traits.

Understanding plant-microbe interaction of rice and soybean with two contrasting diazotrophic bacteria through comparative transcriptome analysis.

Understanding the beneficial plant-microbe interactions is becoming extremely critical for deploying microbes imparting plant fitness and achieving sustainability in agriculture. Diazotrophic bacteria have the unique ability to survive without external sources of nitrogen and simultaneously promote host plant growth, but the mechanisms of endophytic interaction in cereals and legumes have not been studied extensively. We have studied the early interaction of two diazotrophic bacteria, Gluconacetobacter diazotrophicus (GAB) and Bradyrhizobium japonicum (BRH), in 15-day-old seedlings of rice and soybean up to 120 h after inoculation (hai) under low-nitrogen medium. Root colonization of GAB in rice was higher than that of BRH, and BRH colonization was higher in soybean roots as observed from the scanning electron microscopy at 120 hai. Peroxidase enzyme was significantly higher at 24 hai but thereafter was reduced sharply in soybean and gradually in rice. The roots of rice and soybean inoculated with GAB and BRH harvested from five time points were pooled, and transcriptome analysis was executed along with control. Two pathways, "Plant pathogen interaction" and "MAPK signaling," were specific to Rice-Gluconacetobacter (RG), whereas the pathways related to nitrogen metabolism and plant hormone signaling were specific to Rice-Bradyrhizobium (RB) in rice. Comparative transcriptome analysis of the root tissues revealed that several plant-diazotroph-specific differentially expressed genes (DEGs) and metabolic pathways of plant-diazotroph-specific transcripts, viz., chitinase, brassinosteroid, auxin, Myeloblastosis (MYB), nodulin, and nitrate transporter (NRT), were common in all plant-diazotroph combinations; three transcripts, viz., nitrate transport accessory protein (NAR), thaumatin, and thionin, were exclusive in rice and another three transcripts, viz., NAC (NAM: no apical meristem, ATAF: Arabidopsis thaliana activating factor, and CUC: cup-shaped cotyledon), ABA (abscisic acid), and ammonium transporter, were exclusive in soybean. Differential expression of these transcripts and reduction in pathogenesis-related (PR) protein expression show the early interaction. Based on the interaction, it can be inferred that the compatibility of rice and soybean is more with GAB and BRH, respectively. We propose that rice is unable to identify the diazotroph as a beneficial microorganism or a pathogen from an early response. So, it expressed the hypersensitivity-related transcripts along with PR proteins. The molecular mechanism of diazotrophic associations of GAB and BRH with rice vis-à-vis soybean will shed light on the basic understanding of host responses to beneficial microorganisms.

Draft Genome Sequence of Paenibacillus sonchi IIRRBNF1, a Nitrogen-Fixing and Plant Growth-Promoting Bacterium Isolated from Rice Rhizosphere.

Paenibacillus sonchi IIRRBNF1 is a rice-rhizospheric, endospore-forming, Gram-positive, plant growth-promoting rhizobacterium. Here, we report the draft genome sequence of Paenibacillus sonchi IIRRBNF1, which consists of an∼7.3-Mb (7,323,556-bp) genome with 6,271 coding sequences (CDSs), 13 rRNAs, and 67 tRNAs. The genome reveals the presence of a nitrogen-fixing gene cluster and genes associated with multiple plant growth-promoting traits.

Integration of Dual Stress Transcriptomes and Major QTLs from a Pair of Genotypes Contrasting for Drought and Chronic Nitrogen Starvation Identifies Key Stress Responsive Genes in Rice.

We report here the genome-wide changes resulting from low N (N-W+), low water (N+W-)) and dual stresses (N-W-) in root and shoot tissues of two rice genotypes, namely, IR 64 (IR64) and Nagina 22 (N22), and their association with the QTLs for nitrogen use efficiency. For all the root parameters, except for root length under N-W+, N22 performed better than IR64. Chlorophyll a, b and carotenoid content were higher in IR64 under N+W+ treatment and N-W+ and N+W- stresses; however, under dual stress, N22 had higher chlorophyll b content. While nitrite reductase, glutamate synthase (GS) and citrate synthase assays showed better specific activity in IR64, glutamate dehydrogenase showed better specific activity in N22 under dual stress (N-W-); the other N and C assimilating enzymes showed similar but low specific activities in both the genotypes. A total of 8926 differentially expressed genes (DEGs) were identified compared to optimal (N+W+) condition from across all treatments. While 1174, 698 and 903 DEGs in IR64 roots and 1197, 187 and 781 in N22 roots were identified, nearly double the number of DEGs were found in the shoot tissues; 3357, 1006 and 4005 in IR64 and 4004, 990 and 2143 in N22, under N-W+, N+W- and N-W- treatments, respectively. IR64 and N22 showed differential expression in 15 and 11 N-transporter genes respectively, under one or more stress treatments, out of which four showed differential expression also in N+W- condition. The negative regulators of N- stress, e.g., NIGT1, OsACTPK1 and OsBT were downregulated in IR64 while in N22, OsBT was not downregulated. Overall, N22 performed better under dual stress conditions owing to its better root architecture, chlorophyll and porphyrin synthesis and oxidative stress management. We identified 12 QTLs for seed and straw N content using 253 recombinant inbred lines derived from IR64 and N22 and a 5K SNP array. The QTL hotspot region on chromosome 6 comprised of 61 genes, of which, five were DEGs encoding for UDP-glucuronosyltransferase, serine threonine kinase, anthocyanidin 3-O-glucosyltransferase, and nitrate induced proteins. The DEGs, QTLs and candidate genes reported in this study can serve as a major resource for both rice improvement and functional biology.

Deciphering the change in root system architectural traits under limiting and non-limiting phosphorus in Indian bread wheat germplasm.

The root system architectures (RSAs) largely decide the phosphorus use efficiency (PUE) of plants by influencing the phosphorus uptake. Very limited information is available on wheat's RSAs and their deciding factors affecting phosphorus uptake efficiency (PupE) due to difficulties in adopting scoring values used for evaluating root traits. Based on our earlier research experience on nitrogen uptake efficiency screening under, hydroponics and soil-filled pot conditions, a comprehensive study on 182 Indian bread wheat genotypes was carried out under hydroponics with limited P (LP) and non-limiting P (NLP) conditions. The findings revealed a significant genetic variation, root traits correlation, and moderate to high heritability for RSAs traits namely primary root length (PRL), total root length (TRL), total root surface area (TSA), root average diameter (RAD), total root volume (TRV), total root tips (TRT) and total root forks (TRF). In LP, the expressions of TRL, TRV, TSA, TRT and TRF were enhanced while PRL and RAD were diminished. An almost similar pattern of correlations among the RSAs was also observed in both conditions except for RAD. RAD exhibited significant negative correlations with PRL, TRL, TSA, TRT and TRF under LP (r = -0.45, r = -0.35, r = -0.16, r = -0.30, and r = -0.28 respectively). The subclass of TRL, TSA, TRV and TRT representing the 0-0.5 mm diameter had a higher root distribution percentage in LP than NLP. Comparatively wide range of H' value i.e. 0.43 to 0.97 in LP than NLP indicates that expression pattern of these traits are highly influenced by the level of P. In which, RAD (0.43) expression was reduced in LP, and expressions of TRF (0.91) and TSA (0.97) were significantly enhanced. The principal component analysis for grouping of traits and genotypes over LP and NLP revealed a high PC1 score indicating the presence of non-crossover interactions. Based on the comprehensive P response index value (CPRI value), the top five highly P efficient wheat genotypes namely BW 181, BW 103, BW 104, BW 143 and BW 66, were identified. Considering the future need for developing resource-efficient wheat varieties, these genotypes would serve as valuable genetic sources for improving P efficiency in wheat cultivars. This set of genotypes would also help in understanding the genetic architecture of a complex trait like P use efficiency.

Transcriptome Analysis Reveals Important Candidate Genes Related to Nutrient Reservoir, Carbohydrate Metabolism, and Defence Proteins during Grain Development of Hexaploid Bread Wheat and Its Diploid Progenitors.

Wheat grain development after anthesis is an important biological process, in which major components of seeds are synthesised, and these components are further required for germination and seed vigour. We have made a comparative RNA-Seq analysis between hexaploid wheat and its individual diploid progenitors to know the major differentially expressed genes (DEGs) involved during grain development. Two libraries from each species were generated with an average of 55.63, 55.23, 68.13, and 103.81 million reads, resulting in 79.3K, 113.7K, 90.6K, and 121.3K numbers of transcripts in AA, BB, DD, and AABBDD genome species respectively. Number of expressed genes in hexaploid wheat was not proportional to its genome size, but marginally higher than that of its diploid progenitors. However, to capture all the transcripts in hexaploid wheat, sufficiently higher number of reads was required. Functional analysis of DEGs, in all the three comparisons, showed their predominance in three major classes of genes during grain development, i.e., nutrient reservoirs, carbohydrate metabolism, and defence proteins; some of them were subsequently validated through real time quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR). Further, developmental stage-specific gene expression showed most of the defence protein genes expressed during initial developmental stages in hexaploid contrary to the diploids at later stages. Genes related to carbohydrates anabolism expressed during early stages, whereas catabolism genes expressed at later stages in all the species. However, no trend was observed in case of different nutrient reservoirs gene expression. This data could be used to study the comparative gene expression among the three diploid species and homeologue-specific expression in hexaploid.

Root architecture traits variation and nitrate-influx responses in diverse wheat genotypes under different external nitrogen concentrations.

In order to identify the genetic variations in root system architecture traits and their probable association with high- and low-affinity nitrate transport system, we performed several experiments on a genetically diverse set of wheat genotypes grown under two external nitrogen levels (optimum and limited nitrate conditions) at two growth points of the seedling stage. Further, we also examined the nitrate uptake and its transport under different combinations of nitrate availability in the external media using 15N-labelled N-source (15NO3-), and gene expression pattern of different high- and low-affinity nitrate transporters. We observed that nitrate starvation invariably increases the total root size in all genotypes. However, the variation of component traits of total root size under nitrate starvation is genotype-specific at both stages. Further, we also observed genotypic variation in both nitrate uptake and translocation depending on the growth stage, external nitrate concentration and growing conditions. The expression of the TaNRT2.1 gene was invariably up-regulated under low external nitrate concentration; however, it gets reduced after a longer period (21 days) of starvation than the early stage (14 days). Among the four NRT1.1 orthologs, TaNPF6.3 and TaNPF6.4 consistently showed higher expression than TaNPF6.1 and TaNPF6.2 at higher nitrate concentration at both the growth stages. TaNPF6.3 and TaNPF6.4 apparently showed a feature of typical low-affinity nitrate transporter gene at higher external nitrate concentration at 14 and 21 days growth stages, respectively. The present study reveals the complex root system of wheat that has genotype-specific N-foraging along with highly coordinated high- and low-affinity nitrate transport systems for nitrate uptake and transport.

Dominance of recombinant cotton leaf curl Multan-Rajasthan virus associated with cotton leaf curl disease outbreak in northwest India.

Cotton leaf curl disease (CLCuD), caused by whitefly (Bemisiatabaci) transmitted single-stranded DNA viruses belonging to the Genus, Begomovirus (family, Geminiviridae) in association with satellite molecules; is responsible for major economic losses in cotton in three northwest (NW) Indian states Haryana, Punjab, and Rajasthan. Annual CLCuD incidences during 2012 to 2014 were estimated to be 37.5%, 63.6%, and 38.8% respectively. Cotton leaves were collected from symptomatic plants annually for three years and subjected to DNA isolation, followed by rolling circle amplification (RCA), cloning, and DNA sequencing of apparently full-length begomoviral genomes and associated betasatellites and alphasatellites. Among the thirteen CLCuD-begomoviral genomes recovered, eight were identified as Cotton leaf curl Multan virus-Rajasthan (CLCuMuV-Ra), one as -Pakistan (PK) and another as -Faisalabad (Fai), whereas, three were as Cotton leaf curl Kokhran virus-Burewala (CLCuKoV-Bu), indicating that CLCuMuV-Ra was the most prevalent begomovirus species. Five of the eight CLCuMuV-Ra sequences were found to be recombinants. The CLCuMuV-Ra- associated satellites consisted of Cotton leaf curl Multan betasatellite (CLCuMB), and Gossypium darwinii symptomless alphasatellite (GDarSLA), and Croton yellow vein mosaic alphasatellite (CrYVMoA). The second most abundant helper virus species, CLCuKoV-Bu, was associated with CLCuMB and GDarSLA.

Transcriptome data of cultivated tetraploid and hexaploid wheat variety during grain development.

Wheat is a major food crop and an important component of human diet throughout the world. There are two major types of cultivated wheat; one is tetraploid durum (pasta) wheat and another one is hexaploid bread wheat. Wheat grain is the reservoir of two major dietary components - carbohydrate and protein, which get accumulated during seed maturation and directly affects yield and quality. Hexaploid, having 6 copies of each chromosome differs to a great extent from tetraploid having 4 copies of each chromosome. Studying the gene expression pattern in developing grain would help in understanding the difference in metabolic process as well as involvement of the genes in these two types of wheat. A transcriptional comparison of developing grains was carried out between the two wheat genotypes; tetraploid (AABB:PDW233) and hexaploid (AABBDD:PBW343) using RNA-seq. Approximately 194 million raw reads were obtained from both libraries. After removal of contaminations, a huge proportion (>99%), of high quality reads were obtained, were aligned to reference genome. A total of 2324 up-regulated and 522 down-regulated genes were identified as differentially expressed between PDW233 vs PBW343. Gene ontology annotation and enrichment analysis gave further information about differentially expressed genes between durum and bread wheat. This information will help in understanding process grain reserve in tetraploid and hexaploid wheat in relation to their nutritional quality.

Homeologue Specific Gene Expression Analysis of Two Vital Carbon Metabolizing Enzymes-Citrate Synthase and NADP-Isocitrate Dehydrogenase-from Wheat (Triticum aestivum L.) Under Nitrogen Stress : Homeologue Specific gene expression of CS and NADP-ICDH.

Citrate synthase (CS) and NADP-dependent isocitrate dehydrogenase (NADP-ICDH) have been considered as candidate enzymes to provide carbon skeletons for nitrogen assimilation, i.e., production of 2-oxoglutarate required by the glutamine synthetase/glutamate synthase cycle. The CS and NADP-ICDH cDNAs were encoded for polypeptides of 402 and 480 amino acids with an estimated molecular weight of 53.01 and 45 kDa and an isoelectric point of 9.08 and 5.98, respectively. Phylogenetic analysis of these proteins in wheat across kingdoms confirmed the close relationship with Aegilops tauschii and Hordeum vulgare. Further, their amino acid sequences were demonstrated to have some conserved motifs such as Mg2+ or Mn2 binding site, catalytic sites, NADP binding sites, and active sites. In-silico-identified genomic sequences for the three homeologues A, B, and Dof CS and NADP-ICDH were found to be located on long arm of chromosomes 5 and 3, and sequence analysis also revealed that the three homeologues consisted of 13 and 15 exons, respectively. The total expression analysis indicated that both genes are ubiquitously expressed in shoot and root tissues under chronic as well as transient nitrogen stress. However, they are differentially and contrastingly expressed but almost in a coordinated manner in both the tissues. Under chronic as well as transient stress, both the genes in shoot tissue showed downregulation, lowest at 6 h of transient stress. However, in the root tissue, trend was found opposite except with exceptions. Moreover, all the three homeologues of both the genes were transcribed differentially, and the ratio of the individual homeologues transcripts to total homeologues transcripts also varied with the tissue, i.e., shoots or roots, as well as with nitrogen stress treatments. Thus, cDNA as well as genomic sequence information, apparent expression at different time point of nitrogen stress, and coordination between these enzymes would be ultimately linked to nitrate assimilation and nitrogen use efficiency in wheat.