Identification of soybean mosaic virus strain SC7 resistance loci and candidate genes in soybean [Glycine max (L.) Merr.].

Soybean [Glycine max (L.) Merr.] is an important legume crop worldwide, which provides abundant plant protein and oil for human beings. Soybean mosaic virus (SMV) can cause serious damage to the yield and quality of soybean, but it is difficult to control SMV with chemicals, breeding SMV-resistant varieties has become the most effective way to control the disease. Therefore, it is important to identify SMV resistance genes from soybean resources and apply them to soybean breeding. In this study, the disease rates (DRs) of 219 soybean accessions to SMV strain SC7 in two environments were investigated. A high-density NJAU 355 K SoySNP array was used for genome-wide association study (GWAS) of DR. A 274 kb region on chromosome 15 (1,110,567 bp to 1,384,173 bp) was repeatedly detected in two environments. Six new significant single nucleotide polymorphisms (SNPs) on chromosome 15 were identified. Four of these six SNPs were located within two candidate genes, Glyma.15G015700 and Glyma.15G015800. The elite haplotype Glyma.15G015700Hap I with low DR exhibited strong resistance to SC7. The expression of Glyma.15G015700 in the SMV-resistant accession increased significantly after inoculation with SC7. Furthermore, most of the proteins predicted to interact with Glyma.15G015700 are heat shock proteins, which have been shown to be related to disease resistance. In summary, new SMV resistance loci and a new candidate gene, Glyma.15G015700, were identified and might be utilized in further soybean disease resistance breeding.

Understanding the nature of blast resistance in combined bacterial leaf blight and blast gene pyramided lines of rice variety tellahamsa.

BACKGROUND: Rice blast and bacterial leaf blight (BLB) are the most limiting factors for rice production in the world which cause yield losses typically ranging from 20 to 30% and can be as high as 50% in some areas of Asia especially India under severe infection conditions. METHODS AND RESULTS: An improved line of Tellahamsa, TH-625-491 having two BLB resistance genes (xa13 and Xa21) and two blast resistance genes (Pi54 and Pi1) with 95% Tellahamsa genome was used in the present study. TH-625-491 was validated for all four target genes and was used for backcrossing with Tellahamsa. Seventeen IBC1F1 plants heterozygous for all four target genes, 19 IBC1F2 plants homozygous for four, three and two gene combinations and 19 IBC1F2:3 plants also homozygous for four, three and two gene combinations were observed. Among seventeen IBC1F1 plants, IBC1F1-62 plant recorded highest recurrent parent genome (97.5%) covering 75 polymorphic markers. Out of the total of 920 IBC1F2 plants screened, 19 homozygous plants were homozygous for four, three and two target genes along with bacterial blight resistance. Background analysis was done in all 19 homozygous IBC1F2 plants possessing BLB resistance (possessing xa13, Xa21, Pi54 and Pi1 in different combinations) with five parental polymorphic SSR markers. IBC1F2-62-515 recovered 98.5% recurrent parent genome. The four, three and two gene pyramided lines of Tellahamsa exhibited varying resistance to blast. CONCLUSIONS: Results show that there might be presence of antagonistic effect between bacterial blight and blast resistance genes since the lines with Pi54 and Pi1 combination are showing better resistance than the combinations with both bacterial blight and blast resistance genes.

Pangenome characterization and analysis of the NAC gene family reveals genes for Sclerotinia sclerotiorum resistance in sunflower (Helianthus annuus).

BACKGROUND: Sunflower (Helianthus annuus) is one of the most important economic crops in oilseed production worldwide. The different cultivars exhibit variability in their resistance genes. The NAC transcription factor (TF) family plays diverse roles in plant development and stress responses. With the completion of the H. annuus genome sequence, the entire complement of genes coding for NACs has been identified. However, the reference genome of a single individual cannot cover all the genetic information of the species. RESULTS: Considering only a single reference genome to study gene families will miss many meaningful genes. A pangenome-wide survey and characterization of the NAC genes in sunflower species were conducted. In total, 139 HaNAC genes are identified, of which 114 are core and 25 are variable. Phylogenetic analysis of sunflower NAC proteins categorizes these proteins into 16 subgroups. 138 HaNACs are randomly distributed on 17 chromosomes. SNP-based haplotype analysis shows haplotype diversity of the HaNAC genes in wild accessions is richer than in landraces and modern cultivars. Ten HaNAC genes in the basal stalk rot (BSR) resistance quantitative trait loci (QTL) are found. A total of 26 HaNAC genes are differentially expressed in response to Sclerotinia head rot (SHR). A total of 137 HaNAC genes are annotated in Gene Ontology (GO) and are classified into 24 functional groups. GO functional enrichment analysis reveals that HaNAC genes are involved in various functions of the biological process. CONCLUSIONS: We identified NAC genes in H. annuus (HaNAC) on a pangenome-wide scale and analyzed S. sclerotiorum resistance-related NACs. This study provided a theoretical basis for further genomic improvement targeting resistance-related NAC genes in sunflowers.

Precision mapping and expression analysis of recessive bacterial blight resistance gene xa-45(t) from Oryza glaberrima.

BACKGROUND: Bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most devastating diseases of rice leading to huge yield losses in Southeast Asia. The recessive resistance gene xa-45(t) from Oryza glaberrima IRGC102600B, mapped on rice chromosome 8, spans 80 Kb with 9 candidate genes on Nipponbare reference genome IRGSP-1.0. The xa-45(t) gene provides durable resistance against all the ten Xanthomonas pathotypes of Northern India, thus aiding in the expansion of recessive bacterial blight resistance gene pool. Punjab Rice PR127, carrying xa-45(t), was released for wider use in breeding programs. This study aims to precisely locate the target gene among the 9 candidates conferring resistance to bacterial blight disease. METHODS AND RESULTS: Sanger sequencing of all nine candidate genes revealed seven SNPs and an Indel between the susceptible parent Pusa 44 and the resistant introgression line IL274. The genotyping with polymorphic markers identified three recombinant breakpoints for LOC_Os08g42370, and LOC_Os08g42400, 15 recombinants for LOC_Os08g423420 and 26 for LOC_Os08g42440 out of 190 individuals. Relative expression analysis across six time intervals (0, 8, 24, 48, 72, and 96 h) after bacterial blight infection showed over expression of LOC_Os08g42410-specific transcripts in IL274 compared to Pusa 44, with a significant 4.46-fold increase observed at 72 h post-inoculation. CONCLUSIONS: The Indel marker at the locus LOC_Os08g42410 was found co-segregating with the phenotype, suggesting its candidacy towards xa-45(t). The transcript abundance assay provides strong evidence for the involvement of LOC_Os08g42410 in the resistance conferred by the bacterial blight gene xa-45(t).

Expression profiling of Nuclear Factor-Y (NF-Y) transcription factors during dehydration and salt stress in finger millet reveals potential candidate genes for multiple stress tolerance.

MAIN CONCLUSION: Expression profiling of NF-Y transcription factors during dehydration and salt stress in finger millet genotypes contrastingly differing in tolerance levels identifies candidate genes for further characterization and functional studies. The Nuclear Factor-Y (NF-Y) transcription factors are known for imparting abiotic stress tolerance in different plant species. However, there is no information on the role of this transcription factor family in naturally drought-tolerant crop finger millet (Eleusine coracana L.). Therefore, interpretation of expression profiles against drought and salinity stress may provide valuable insights into specific and/or overlapping expression patterns of Eleusine coracana Nuclear Factor-Y (EcNF-Y) genes. Given this, we identified 59 NF-Y (18 NF-YA, 23 NF-YB, and 18 NF-YC) encoding genes and designated them EcNF-Y genes. Expression profiling of these genes was performed in two finger millet genotypes, PES400 (dehydration and salt stress tolerant) and VR708 (dehydration and salt stress sensitive), subjected to PEG-induced dehydration and salt (NaCl) stresses at different time intervals (0, 6, and 12 h). The qRT-PCR expression analysis reveals that the six EcNF-Y genes namely EcNF-YA1, EcNF-YA5, EcNF-YA16, EcNF-YB6, EcNF-YB10, and EcNF-YC2 might be associated with tolerance to both dehydration and salinity stress in early stress condition (6 h), suggesting the involvement of these genes in multiple stress responses in tolerant genotype. In contrast, the transcript abundance of finger millet EcNF-YA5 genes was also observed in the sensitive genotype VR708 under late stress conditions (12 h) of both dehydration and salinity stress. Therefore, the EcNF-YA5 gene might be important for adaptation to salinity and dehydration stress in sensitive finger millet genotypes. Therefore, this gene could be considered as a susceptibility determinant, which can be edited to impart tolerance. The phylogenetic analyses revealed that finger millet NF-Y genes share strong evolutionary and functional relationship to NF-Ys governing response to abiotic stresses in rice, sorghum, maize, and wheat. This is the first report of expression profiling of EcNF-Ys genes identified from the finger millet genome and reveals potential candidate for enhancing dehydration and salt tolerance.

Identification of Quantitative Trait Loci and Candidate Genes Controlling Seed Dormancy in Eggplant (Solanum melongena L.).

Seed dormancy is a life adaptation trait exhibited by plants in response to environmental changes during their growth and development. The dormancy of commercial seeds is the key factor affecting seed quality. Eggplant seed dormancy is controlled by quantitative trait loci (QTLs), but reliable QTLs related to eggplant dormancy are still lacking. In this study, F2 populations obtained through the hybridization of paternally inbred lines with significant differences in dormancy were used to detect regulatory sites of dormancy in eggplant seeds. Three QTLs (dr1.1, dr2.1, and dr6.1) related to seed dormancy were detected on three chromosomes of eggplant using the QTL-Seq technique. By combining nonsynonymous sites within the candidate regions and gene functional annotation analysis, nine candidate genes were selected from three QTL candidate regions. According to the germination results on the eighth day, the male parent was not dormant, but the female parent was dormant. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the expression of nine candidate genes, and the Smechr0201082 gene showed roughly the same trend as that in the phenotypic data. We proposed Smechr0201082 as the potential key gene involved in regulating the dormancy of eggplant seeds. The results of seed experiments with different concentrations of gibberellin A3 (GA3) showed that, within a certain range, the higher the gibberellin concentration, the earlier the emergence and the higher the germination rate. However, higher concentrations of GA3 may have potential effects on eggplant seedlings. We suggest the use of GA3 at a concentration of 200-250 mg·L-1 to treat dormant seeds. This study provides a foundation for the further exploration of genes related to the regulation of seed dormancy and the elucidation of the molecular mechanism of eggplant seed dormancy and germination.

Fine mapping of TFL, a major gene regulating fruit length in snake gourd (Trichosanthes anguina L).

Fruit length is a crucial agronomic trait of snake gourd (Trichosanthes anguina L); however, genes associated with fruit length have not been characterised. In this study, F2 snake gourd populations were generated by crossing the inbred lines, S1 and S2 (fruit lengths: 110 and 20 cm, respectively). Subsequently, bulk segregant analysis, sequencing, and fine-mapping were performed on the F2 population to identify target genes. Our findings suggest that the fruit length of snake gourd is regulated by a major-effect regulatory gene. Mining of genes regulating fruit length in snake gourd to provide a basis for subsequent selection and breeding of new varieties. Genotype-phenotype association analysis was performed on the segregating F2 population comprising 6,000 plants; the results indicate that the target gene is located on Chr4 (61,846,126-61,865,087 bp, 18.9-kb interval), which only carries the annotated candidate gene, Tan0010544 (designated TFL). TFL belongs to the MADS-box family, one of the largest transcription factor families. Sequence analysis revealed a non-synonymous mutation of base C to G at position 202 in the coding sequence of TFL, resulting in the substitution of amino acid Gln to Glu at position 68 in the protein sequence. Subsequently, an InDel marker was developed to aid the marker-assisted selection of TFL. The TFL in the expression parents within the same period was analysed using quantitative real-time PCR; the TFL expression was significantly higher in short fruits than long fruits. Therefore, TFL can be a candidate gene for determining the fruit length in snake gourd. Collectively, these findings improve our understanding of the genetic components associated with fruit length in snake gourds, which could aid the development of enhanced breeding strategies for plant species.

Identification and expression analyses of B3 genes reveal lineage-specific evolution and potential roles of REM genes in pepper.

BACKGROUND: The B3 gene family, one of the largest plant-specific transcription factors, plays important roles in plant growth, seed development, and hormones. However, the B3 gene family, especially the REM subfamily, has not been systematically and functionally studied. RESULTS: In this study, we performed genome-wide re-annotation of B3 genes in five Solanaceae plants, Arabidopsis thaliana, and Oryza sativa, and finally predicted 1,039 B3 genes, including 231 (22.2%) newly annotated genes. We found a striking abundance of REM genes in pepper species (Capsicum annuum, Capsicum baccatum, and Capsicum chinense). Comparative motif analysis revealed that REM and other subfamilies (ABI3/VP1, ARF, RAV, and HSI) consist of different amino acids. We verified that the large number of REM genes in pepper were included in the specific subgroup (G8) through the phylogenetic analysis. Chromosome location and evolutionary analyses suggested that the G8 subgroup genes evolved mainly via a pepper-specific recent tandem duplication on chromosomes 1 and 3 after speciation between pepper and other Solanaceae. RNA-seq analyses suggested the potential functions of REM genes under salt, heat, cold, and mannitol stress conditions in pepper (C. annuum). CONCLUSIONS: Our study provides evolutionary and functional insights into the REM gene family in pepper.

The microRNA miR482 regulates NBS-LRR genes in response to ALT1 infection in apple.

Plants are frequently attacked by a variety of pathogens and thus have evolved a series of defense mechanisms, one important mechanism is resistance gene (R gene)-mediated disease resistance, but its expression is tightly regulated. NBS-LRR genes are the largest gene family of R genes. microRNAs (miRNAs) target to a number of NBS-LRR genes and trigger the production of phased small interfering RNAs (phasiRNAs) from these transcripts. phasiRNAs cis or trans regulate NBS-LRR genes, which can result in the repression of R gene expression. In this study, we screened for upregulated miR482 in the susceptible apple cultivar 'Golden Delicious' (GD) after inoculation with the fungal pathogen Alternaria alternata f. sp. mali (ALT1). Additionally, through combined degradome sequencing, we identified a gene targeted by miR482, named MdTNL1, a gene encoding a TIR-NBS-LRR (Toll/interleukin1 receptor-nucleotide binding site-leucine-rich repeat) protein. This gene exhibited a significant down-regulation post ALT1 inoculation, suggesting an impact on gene expression mediated by miRNA regulation. miR482 could cleave MdTNL1 and generate phasiRNAs at the cleavage site. We found that overexpression of miR482 inhibited the expression of MdTNL1 and thus reduced the disease resistance of GD, while silencing of miR482 increased the expression of MdTNL1 and thus improved the disease resistance of GD. This work elucidates key mechanisms underlying the immune response to Alternaria infection in apple. Identification of the resistance genes involved will enable molecular breeding for prevention and control of Alternaria leaf spot disease in this important fruit crop.

Contiguous identity between entire coding regions of transgenic and native genes rather than special regions is essential for a strong co-suppression.

The discovery of co-suppression in plants has greatly boosted the study of gene silencing mechanisms, but its triggering mechanism has remained a mystery. In this study, we explored its possible trigger mechanism by using Fatty acid desaturase 2 (FAD2) and Fatty acid elongase 1 (FAE1) strong co-suppression systems. Analysis of small RNAs in FAD2 co-suppression lines showed that siRNAs distributed throughout the coding region of FAD2 with an accumulated peak. However, mutations of the peak siRNA-matched site and siRNA derived site had not alleviated the co-suppression of its transgenic lines. Synthetic FAD2 (AtFAD2sm), which has synonymous mutations in the entire coding region, failed to trigger any co-suppression. Furthermore, 5' and 3' portions of AtFAD2 and AtFAD2sm were swapped to form two hybrid genes, AtFAD2-3sm and AtFAD2-5sm. 80 % and 92 % of their transgenic lines exhibited co-suppression, respectively. Finally, FAE1s with different degrees of the continuous sequence identity compared with AtFAE1 were tested in their Arabidopsis transgenic lines, and the results showed the co-suppression frequency was reduced as their continuous sequence identity stepped down. This work suggests that contiguous identity between the entire coding regions of transgenic and native genes rather than a special region is essential for a strong co-suppression.

GIGANTEA accelerates wheat heading time through gene interactions converging on FLOWERING LOCUS T1.

Precise regulation of flowering time is critical for cereal crops to synchronize reproductive development with optimum environmental conditions, thereby maximizing grain yield. The plant-specific gene GIGANTEA (GI) plays an important role in the control of flowering time, with additional functions on the circadian clock and plant stress responses. In this study, we show that GI loss-of-function mutants in a photoperiod-sensitive tetraploid wheat background exhibit significant delays in heading time under both long-day (LD) and short-day photoperiods, with stronger effects under LD. However, this interaction between GI and photoperiod is no longer observed in isogenic lines carrying either a photoperiod-insensitive allele in the PHOTOPERIOD1 (PPD1) gene or a loss-of-function allele in EARLY FLOWERING 3 (ELF3), a known repressor of PPD1. These results suggest that the normal circadian regulation of PPD1 is required for the differential effect of GI on heading time in different photoperiods. Using crosses between mutant or transgenic plants of GI and those of critical genes in the flowering regulation pathway, we show that GI accelerates wheat heading time by promoting FLOWERING LOCUS T1 (FT1) expression via interactions with ELF3, VERNALIZATION 2 (VRN2), CONSTANS (CO), and the age-dependent microRNA172-APETALA2 (AP2) pathway, at both transcriptional and protein levels. Our study reveals conserved GI mechanisms between wheat and Arabidopsis but also identifies specific interactions of GI with the distinctive photoperiod and vernalization pathways of the temperate grasses. These results provide valuable knowledge for modulating wheat heading time and engineering new varieties better adapted to a changing environment.

Green Revolution dwarfing Rht genes negatively affected wheat floral traits related to cross-pollination efficiency.

Hybrid breeding is a promising strategy to quickly improve wheat yield and stability. Due to the usefulness of the Rht 'Green Revolution' dwarfing alleles, it is important to gain a better understanding of their impact on traits related to hybrid development. Traits associated with cross-pollination efficiency were studied using Near Isogenic Lines carrying the different sets of alleles in Rht genes: Rht1 (semi-dwarf), Rht2 (semi-dwarf), Rht1 + 2 (dwarf), Rht3 (extreme dwarf), Rht2 + 3 (extreme dwarf), and rht (tall) during four growing seasons. Results showed that the extreme dwarfing alleles Rht2 + 3, Rht3, and Rht1 + 2 presented the greatest effects in all the traits analyzed. Plant height showed reductions up to 64% (Rht2 + 3) compared to rht. Decreases up to 20.2% in anther length and 33% in filament length (Rht2 + 3) were observed. Anthers extrusion decreased from 40% (rht) to 20% (Rht1 and Rht2), 11% (Rht3), 8.3% (Rht1 + 2), and 6.5% (Rht2 + 3). Positive correlations were detected between plant height and anther extrusion, anther, and anther filament lengths, suggesting the negative effect of dwarfing alleles. Moreover, the magnitude of these negative impacts depends on the combination of the alleles: Rht2 + 3 > Rht3/Rht1 + 2 > Rht2/Rht1 > rht (tall). Reductions were consistent across genotypes and environments with interactions due to magnitude effects. Our results indicate that Rht alleles are involved in multiple traits of interest for hybrid wheat production and the need to select alternative sources for reduced height/lodging resistance for hybrid breeding programs.

Profiling of the gene expression and alternative splicing landscapes of Eucalyptus grandis.

Eucalyptus is a widely planted hardwood tree species due to its fast growth, superior wood properties and adaptability. However, the post-transcriptional regulatory mechanisms controlling tissue development and stress responses in Eucalyptus remain poorly understood. In this study, we performed a comprehensive analysis of the gene expression profile and the alternative splicing (AS) landscape of E. grandis using strand-specific RNA-Seq, which encompassed 201 libraries including different organs, developmental stages, and environmental stresses. We identified 10 416 genes (33.49%) that underwent AS, and numerous differentially expressed and/or differential AS genes involved in critical biological processes, such as primary-to-secondary growth transition of stems, adventitious root formation, aging and responses to phosphorus- or boron-deficiency. Co-expression analysis of AS events and gene expression patterns highlighted the potential upstream regulatory role of AS events in multiple processes. Additionally, we highlighted the lignin biosynthetic pathway to showcase the potential regulatory functions of AS events in the KNAT3 and IRL3 genes within this pathway. Our high-quality expression atlas and AS landscape serve as valuable resources for unravelling the genetic control of woody plant development, long-term adaptation, and understanding transcriptional diversity in Eucalyptus. Researchers can conveniently access these resources through the interactive ePlant browser (https://bar.utoronto.ca/eplant_eucalyptus).

Identification and function analysis of GABA branch three gene families in the cotton related to abiotic stresses.

γ -aminobutyric acid (GABA) is closely related to the growth, development and stress resistance of plants. Combined with the previous study of GABA to promote the cotton against abiotic stresses, the characteristics and expression patterns of GABA branch gene family laid the foundation for further explaining its role in cotton stress mechanism. Members of GAD, GAB-T and SSADH (three gene families of GABA branch) were identified from the Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum and Gossypium raimondii genome. The GABA branch genes were 10 GAD genes, 4 GABA-T genes and 2 SSADH genes. The promoter sequences of genes mainly contains response-related elements such as light, hormone and environment.Phylogenetic analysis shows that GAD indicating that even in the same species, the homologous sequences in the family. The GABA-T gene of each cotton genus was in sum the family had gene loss in the process of dicotyledon evolution. SSADH families Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum and Gossypium raimondii were closely related to the dicot plants.GABA gene is involved in the regulation of salt stress and high temperature in Gossypium hirsutum.GABA attenuated part of the abiotic stress damage by increasing leaf protective enzyme activity and reducing reactive oxygen species production.This lays the foundation for a thorough analysis of the mechanism of GABA in cotton stress resistance.

Dissection of a rapidly evolving wheat resistance gene cluster by long-read genome sequencing accelerated the cloning of Pm69.

Gene cloning in repeat-rich polyploid genomes remains challenging. Here, we describe a strategy for overcoming major bottlenecks in cloning of the powdery mildew resistance gene (R-gene) Pm69 derived from tetraploid wild emmer wheat. A conventional positional cloning approach was not effective owing to suppressed recombination. Chromosome sorting was compromised by insufficient purity. A Pm69 physical map, constructed by assembling Oxford Nanopore Technology (ONT) long-read genome sequences, revealed a rapidly evolving nucleotide-binding leucine-rich repeat (NLR) R-gene cluster with structural variations. A single candidate NLR was identified by anchoring RNA sequencing reads from susceptible mutants to ONT contigs and was validated by virus-induced gene silencing. Pm69 is likely a newly evolved NLR and was discovered in only one location across the wild emmer wheat distribution range in Israel. Pm69 was successfully introgressed into cultivated wheat, and a diagnostic molecular marker was used to accelerate its deployment and pyramiding with other R-genes.

GWAS identifies two important genes involved in Chinese chestnut weight and leaf length regulation.

There are many factors that affect the yield of Chinese chestnut (Castanea mollissima), with single nut weight (SNW) being one of the most important. Leaf length is also related to Chinese chestnut yield. However, the genetic architecture and gene function associated with Chinese chestnut nut yield have not been fully explored. In this study, we performed genotyping by sequencing 151 Chinese chestnut cultivars, followed by a genome-wide association study (GWAS) on six horticultural traits. First, we analyzed the phylogeny of the Chinese chestnut and found that the Chinese chestnut cultivars divided into two ecotypes, a northern and southern cultivar group. Differences between the cultivated populations were found in the pathways of plant growth and adaptation to the environment. In the selected regions, we also found interesting tandemly arrayed genes that may influence Chinese chestnut traits and environmental adaptability. To further investigate which horticultural traits were selected, we performed a GWAS using six horticultural traits from 151 cultivars. Forty-five loci that strongly associated with horticultural traits were identified, and six genes highly associated with these traits were screened. In addition, a candidate gene associated with SNW, APETALA2 (CmAP2), and another candidate gene associated with leaf length (LL), CRYPTOCHROME INTERACTING BASIC HELIX-LOOP-HELIX 1 (CmCIB1), were verified in Chinese chestnut and Arabidopsis (Arabidopsis thaliana). Our results showed that CmAP2 affected SNW by negatively regulating cell size. CmCIB1 regulated the elongation of new shoots and leaves by inducing cell elongation, potentially affecting photosynthesis. This study provided valuable information and insights for Chinese chestnut breeding research.

Disruption of the rice ALS1 localized in chloroplast causes seedling-lethal albino phenotype.

Chloroplasts are the organelles responsible for photosynthesis and regulate normal plant growth. Although translation elongation factors play important roles in chloroplast development, functional studies of chloroplast translation elongation factors in higher plants remain very sparse. Here, we obtained a rice mutant exhibiting seedling-lethal albino phenotype and named it albino and lethal seedling 1 (als1). Consistently, low content of photosynthetic pigments, malformed chloroplasts and defective photosynthesis were observed in als1 mutant leaves. Map-based cloning experiment showed that als1 mutant had a T base insertion in Os02g0595700, causing a frame shift and premature stop codon. ALS1 encoded a GTP-binding protein EF-Tu, which acts as a translation elongation factor in chloroplast protein translation. ALS1 was found to be expressed throughout plant with highest expression level in young leaves. Moreover, ALS1 was located in chloroplast, whereas the truncated als1 could not normally be located in chloroplast. Additionally, the ALS1 mutation significantly influenced the expression of downstream genes, such as genes relevant to chlorophyll biosynthesis, photosynthesis as well as chloroplast development. These results show that ALS1 acts as a key regulator of chloroplast development and plant growth.

Overexpression of SlCRF6 in tomato inhibits leaf development and affects plant morphology.

Cytokinin response factors (CRFs) are transcription factors (TFs) that are specific to plants and have diverse functions in plant growth and stress responses. However, the precise roles of CRFs in regulating tomato plant architecture and leaf development have not been comprehensively investigated. Here, we identified a novel CRF, SlCRF6, which is involved in the regulation of plant growth via the gibberellin (GA) signaling pathway. SlCRF6-overexpressing (SlCRF6-OE) plants displayed pleiotropic phenotypic changes, including reduced internode length and leaf size, which caused dwarfism in tomato plants. This dwarfism could be alleviated by application of exogenous GA3. Remarkably, quantitative real-time PCR (qRTPCR), a dual luciferase reporter assay and a yeast one-hybrid (Y1H) assay revealed that SlCRF6 promoted the expression of SlDELLA (a GA signal transduction inhibitor) in vivo. Furthermore, transgenic plants displayed variegated leaves and diminished chlorophyll content, resulting in decreased photosynthetic efficiency and less starch than in wild-type (WT) plants. The results of transient expression assays and Y1H assays indicated that SlCRF6 suppressed the expression of SlPHAN (leaf morphology-related gene). Collectively, these findings suggest that SlCRF6 plays a crucial role in regulating tomato plant morphology, leaf development, and the accumulation of photosynthetic products.

Integrated analysis of HSP20 genes in the developing flesh of peach: identification, expression profiling, and subcellular localization.

BACKGROUND: Plant HSP20s are not only synthesized in response to heat stress but are also involved in plant biotic and abiotic stress resistance, normal metabolism, development, differentiation, survival, ripening, and death. Thus, HSP20 family genes play very important and diverse roles in plants. To our knowledge, HSP20 family genes in peach have not yet been characterized in detail, and little is known about their possible function in the development of red flesh in peach. RESULTS: In total, 44 PpHSP20 members were identified in the peach genome in this study. Forty-four PpHSP20s were classified into 10 subfamilies, CI, CII, CIII, CV, CVI, CVII, MII, CP, ER, and Po, containing 18, 2, 2, 10, 5, 1, 1, 2, 1, and 2 proteins, respectively. Among the 44 PpHSP20 genes, 6, 4, 4, 3, 7, 11, 5, and 4 PpHSP20 genes were located on chromosomes 1 to 8, respectively. In particular, approximately 15 PpHSP20 genes were located at both termini or one terminus of each chromosome. A total of 15 tandem PpHSP20 genes were found in the peach genome, which belonged to five tandemly duplicated groups. Overall, among the three cultivars, the number of PpHSP20 genes with higher expression levels in red flesh was greater than that in yellow or white flesh. The expression profiling for most of the PpHSP20 genes in the red-fleshed 'BJ' was higher overall at the S3 stage than at the S2, S4-1, and S4-2 stages, with the S3 stage being a very important period of transformation from a white color to the gradual anthocyanin accumulation in the flesh of this cultivar. The subcellular localizations of 16 out of 19 selected PpHSP20 proteins were in accordance with the corresponding subfamily classification and naming. Additionally, to our knowledge, Prupe.3G034800.1 is the first HSP20 found in plants that has the dual targets of both the endoplasmic reticulum and nucleus. CONCLUSIONS: This study provides a comprehensive understanding of PpHSP20s, lays a foundation for future analyses of the unknown function of PpHSP20 family genes in red-fleshed peach fruit and advances our understanding of plant HSP20 genes.

RNA-Sequencing Analysis Revealed Genes Associated with Sweet Potato (Ipomoea batatas (L.) Lam.) Responses to Stem Rot during Different Infection Stages.

The sweet potato, which is an important tuber crop in China, is susceptible to a variety of pathogens and insect pests during cultivation and production. Stem rot is a common sweet potato disease that seriously affects tuber yield and quality. Unfortunately, there have been relatively few studies on the mechanism mediating the stem rot resistance of sweet potatoes. In this study, a transcriptome sequencing analysis was completed using Xushu 48 samples at different stages (T1, T2, and T3) of the stem rot infection. The T1 vs. T2, T1 vs. T3, and T2 vs. T3 comparisons detected 44,839, 81,436, and 61,932 differentially expressed genes (DEGs), respectively. The DEGs encoded proteins primarily involved in alanine, aspartate, and glutamate metabolism (ko00250), carbon fixation in photosynthetic organisms (ko00710), and amino sugar and nucleotide sugar metabolism (ko00520). Furthermore, some candidate genes induced by phytopathogen infections were identified, including gene-encoding receptor-like protein kinases (RLK5 and RLK7), an LRR receptor-like serine/threonine protein kinase (SERK1), and transcription factors (bHLH137, ERF9, MYB73, and NAC053). The results of this study provide genetic insights that are relevant to future explorations of sweet potato stem rot resistance, while also providing the theoretical basis for breeding sweet potato varieties that are resistant to stem rot and other diseases.