At the crossroads: strigolactones mediate changes in cytokinin synthesis and signalling in response to nitrogen limitation.

Strigolactones (SLs) are key regulators of shoot growth and responses to environmental stimuli. Numerous studies have indicated that nitrogen (N) limitation induces SL biosynthesis, suggesting that SLs may play a pivotal role in coordinating systemic responses to N availability, but this idea has not been clearly demonstrated. Here, we generated triple knockout mutants in the SL synthesis gene TaDWARF17 (TaD17) in bread wheat and investigated their phenotypic and transcriptional responses under N limitation, aiming to elucidate the role of SLs in the adaptation to N limitation. Tad17 mutants display typical SL mutant phenotypes, and fail to adapt their shoot growth appropriately to N. Despite exhibiting an increased tillering phenotype, Tad17 mutants continued to respond to N limitation by reducing tiller number, suggesting that SLs are not the sole regulators of tillering in response to N availability. RNA-seq analysis of basal nodes revealed that the loss of D17 significantly altered the transcriptional response of N-responsive genes, including changes in the expression profiles of key N response master regulators. Crucially, our findings suggest that SLs are required for the transcriptional downregulation of cytokinin (CK) synthesis and signalling in response to N limitation. Collectively, our results suggest that SLs are essential for the appropriate morphological and transcriptional adaptation to N limitation in wheat, and that the repressive effect of SLs on shoot growth is partly mediated by their repression of CK synthesis.

Understanding the responses of tillering to 2,4-D isooctyl ester in Setaria viridis L.

BACKGROUND: Green foxtail [Setaria viridis (L.)] is one of the most abundant and troublesome annual grass weeds in alfalfa fields in Northeast China. Synthetic auxin herbicide is widely used in agriculture, while how auxin herbicide affects tillering on perennial grass weeds is still unclear. A greenhouse experiment was conducted to examine the effects of auxin herbicide 2,4-D on green foxtail growth, especially on tillers. RESULTS: In the study, 2,4-D isooctyl ester was used. There was an inhibition of plant height and fresh weight on green foxtail after application. The photosynthetic rate of the leaves was dramatically reduced and there was an accumulation of malondialdehyde (MDA) content. Moreover, applying 2,4-D isooctyl ester significantly reduced the tillering buds at rates between 2100 and 8400 ga. i. /ha. Transcriptome results showed that applying 2,4-D isooctyl ester on leaves affected the phytohormone signal transduction pathways in plant tillers. Among them, there were significant effects on auxin, cytokinin, abscisic acid (ABA), gibberellin (GA), and brassinosteroid signaling. Indeed, external ABA and GA on leaves also limited tillering in green foxtail. CONCLUSIONS: These data will be helpful to further understand the responses of green foxtail to 2, 4-D isooctyl ester, which may provide a unique perspective for the development and identification of new target compounds that are effective against this weed species.

TaSPL6B, a member of the Squamosa promoter binding protein-like family, regulates shoot branching and florescence in Arabidopsis thaliana.

BACKGROUND: Squamosa promoter-binding protein-like (SPL) proteins are essential to plant growth and development as plant-specific transcription factors. However, the functions of SPL proteins in wheat need to be further explored. RESULTS: We cloned and characterized TaSPL6B of wheat in this study. Analysis of physicochemical properties revealed that it contained 961 amino acids and had a molecular weight of 105 kDa. Full-length TaSPL6B transcription activity was not validated in yeast and subcellular localization analysis revealed that TaSPL6B was distributed in the nucleus. Ectopic expression of TaSPL6B in Arabidopsis led to increasing number of branches and early flowering. TaSPL6B was highly transcribed in internodes of transgenic Arabidopsis. The expression of AtSMXL6/AtSMXL7/AtSMXL8 (homologous genes of TaD53) was markedly increased, whereas the expression of AtSPL2 (homologous genes of TaSPL3) and AtBRC1 (homologous genes of TaTB1) was markedly reduced in the internodes of transgenic Arabidopsis. Besides, TaSPL6B, TaSPL3 and TaD53 interacted with one another, as demonstrated by yeast two-hybrid and bimolecular fluorescence complementation assays. Therefore, we speculated that TaSPL6B brought together TaD53 and TaSPL3 and enhanced the inhibition effect of TaD53 on TaSPL3 through integrating light and strigolactone signaling pathways, followed by suppression of TaTB1, a key repressor of tillering. CONCLUSIONS: As a whole, our findings contribute to a better understanding of how SPL genes work in wheat and will be useful for further research into how TaSPL6B affects yield-related traits in wheat.

Influence of leaf inclination angle and tillering on population transpiration, soil evaporation, and yield in winter wheat near-isogenic lines.

Leaf inclination angle (LIA) and tillering impact the winter wheat (Triticum aestivum L.) population canopy structure. Understanding their effects on water use (WU) parameters and yield can guide water-saving strategies through population control. In this study, six near-isogenic lines (NILs) and their parents were selected as materials. These special materials were characterized by varying tillering at the current sowing density, a similar genetic background, and, particularly, a gradient in mean flag leaf LIA. The investigation focused on the jointing to early grain-filling stage, the peak water requirement period of wheat crops. Population-scale transpiration (PT) and evaporation from the soil surface (E) were partitioned from total evapotranspiration (ET) by the means of micro-lysimeters. The results showed decreased PT, E, and ET with increased population density (PD) within a narrow density range derived from varying tillering across genotypes. Significant correlations existed between PD and ET, E, and PT, especially in the wettest 2017-2018 growing season. Within such narrow PD range, all the correlations between WU parameters and PD were negative, although some correlations were not statistically significant, thereby suggesting the population structure's predominant impact. No significant correlation existed between LIA and both ET and PT within the LIA range of 35°-65°. However, significant correlations occurred between LIA and E in two growing seasons. Genotypes with similar LIA but different PD produced varied ET; while with similar PD, the four pairs of genotypes with different LIA each consumed similar ET, thus highlighting PD's more crucial role in regulating ET. The yield increased with higher LIA, and showed a significant correlation, emphasizing the LIA's significant effect on yield. However, no correlation was observed with PD, indicating the minor effect of tillering at the current sowing density. Therefore these results might offer valuable insights for breeding water-saving cultivars and optimizing population structures for effective field water conservation.

[Effects of phosphorus application rate on distribution of 13C assimilates and spike formation in different til-lers of wheat with supplementary irrigation]. / 补灌条件下施磷量对小麦不同茎蘖13CåŒåŒ–ç‰©åˆ†é åŠå ¶æˆç©—çš„å½±å“.

To clarify the appropriate rate of phosphorus application and physiological mechanism for promoting wheat tillering and efficient utilization of phosphorus fertilizer with supplementary irrigation, we used 'Jimai 22' wheat variety as the test material, to set up three phosphorus application treatments, including low (90 kg P2O5·hm-2, P1), medium (135 kg P2O5·hm-2, P2), and high (180 kg P2O5·hm-2, P3) application rates, with no phosphorus application as the control (P0). We increased the relative soil water content of each treatment at join-ting stage and anthesis stage to 70%, and measured the area of tiller node, the content of endogenous hormones, the number of tillers in each tiller position, photosynthetic parameters, the distribution of 13C assimilates in each stem and tiller, as well as the grain yield and partial productivity of phosphate fertilizer. The results showed that compared with P0 and P1 treatments, P2 significantly increased the area of tiller node and the trans-zeatin (tZ), the photosynthetic parameters of the uppermost expanded leaves of the main stem, the total tillers per plant, and the distribution of 13C assimilates in each tiller. The number of ears per plant was increased by 0.51 and 0.36, and grain yield was increased by 40.3% and 13.2%, respectively. In P3 treatment, the number of tillers increased, but the panicles per plant, and the grain yield and phosphate fertilizer partial productivity decreased. Our results suggested that the moderate phosphorus treatment (135 kg·hm-2) under supplementary irrigation was suitable for high yield and high efficiency of wheat.

Enhancing Wheat Growth, Physiology, Yield, and Water Use Efficiency under Deficit Irrigation by Integrating Foliar Application of Salicylic Acid and Nutrients at Critical Growth Stages.

Transitioning from full to deficit irrigation (DI) has become a key strategy in arid regions to combat water scarcity and enhance irrigation water use efficiency (IWUE). However, implementing DI requires additional approaches to counter its negative effects on wheat production. One effective approach is the foliar application of salicylic acid (SA), micronutrients (Mic; zinc and manganese), and macronutrients (Mac; nitrogen, phosphorus, and potassium). However, there is a lack of knowledge on the optimal combinations and timing of foliar application for these components to maximize their benefits under arid conditions, which is the primary focus of this study. A two-year field study was conducted to assess the impact of the foliar application of SA alone and in combination with Mic (SA + Mic) or Mic and Mac (SA + Mic + Mac) at various critical growth stages on wheat growth, physiology, productivity, and IWUE under DI conditions. Our result demonstrated that the foliar application of different components, the timing of application, and their interaction had significant effects on all investigated wheat parameters with few exceptions. Applying different components through foliar application at multiple growth stages, such as tillering and heading or tillering, heading, and grain filling, led to significant enhancements in various wheat parameters. The improvements ranged from 7.7% to 23.2% for growth parameters, 8.7% to 24.0% for physiological traits, 1.4% to 21.0% for yield and yield components, and 14.8% to 19.0% for IWUE compared to applying the components only at the tillering stage. Plants treated with different components (SA, Mic, Mac) exhibited enhanced growth, production, and IWUE in wheat compared to untreated plants. The most effective treatment was SA + Mic, followed by SA alone and SA + Mic + Mac. The foliar application of SA, SA + Mic, and SA + Mic + Mac improved growth parameters by 1.2-50.8%, 2.7-54.6%, and 2.5-43.9%, respectively. Yield parameters were also enhanced by 1.3-33.0%, 2.4-37.2%, and 3.0-26.6% while IWUE increased by 28.6%, 33.0%, and 18.5% compared to untreated plants. A heatmap analysis revealed that the foliar application of SA + Mic at multiple growth stages resulted in the highest values for all parameters, followed by SA alone and SA + Mic + Mac applications at multiple growth stages. The lowest values were observed in untreated plants and with the foliar application of different components only at the tillering stage. Thus, this study suggested that the foliar application of SA + Mic at various growth stages can help sustain wheat production in arid regions with limited water resources.

A novel regulator of wheat tillering LT1 identified by using an upgraded BSA method, uni-BSA.

Branching/tillering is a critical process for plant architecture and grain yield. However, Branching is intricately controlled by both endogenous and environmental factors. The underlying mechanisms of tillering in wheat remain poorly understood. In this study, we identified Less Tiller 1 (LT1) as a novel regulator of wheat tillering using an enhanced bulked segregant analysis (BSA) method, uni-BSA. This method effectively reduces alignment noise caused by the high repetitive sequence content in the wheat genome. Loss-of-function of LT1 results in fewer tillers due to defects in axillary meristem initiation and bud outgrowth. We mapped LT1 to a 6 Mb region on the chromosome 2D short arm and validated a nucleotide-binding (NB) domain encoding gene as LT1 using CRISPR/Cas9. Furthermore, the lower sucrose concentration in the shoot bases of lt1 might result in inadequate bud outgrowth due to disturbances in the sucrose biosynthesis pathways. Co-expression analysis suggests that LT1 controls tillering by regulating TaROX/TaLAX1, the ortholog of the Arabidopsis tiller regulator REGULATOR OF AXILLARY MERISTEM FORMATION (ROX) or the rice axillary meristem regulator LAX PANICLE1 (LAX1). This study not only offers a novel genetic resource for cultivating optimal plant architecture but also underscores the importance of our innovative BSA method. This uni-BSA method enables the swift and precise identification of pivotal genes associated with significant agronomic traits, thereby hastening gene cloning and crop breeding processes in wheat. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01484-7.

Screening of sugarcane germplasm against Sporisorium scitamineum and its effects on setts germination and tillering.

Sugarcane smut is the most damaging disease that is present almost across the globe, causing mild to severe yield losses depending upon the cultivar types, pathogen races and climatic conditions. Cultivation of smut-resistant cultivars is the most feasible and economical option to mitigate its damages. Previous investigations revealed that there is a scarcity of information on early detection and effective strategies to suppress etiological agents of smut disease due to the characteristics overlapping within species complexes. In this study, 104 sugarcane cultivars were screened by artificial inoculation with homogenate of all possible pathogen races of Sporisorium scitamineum during two consecutive growing seasons. The logistic smut growth pattern and the disease intrinsic rate were recorded by disease growth curve. Variable levels of disease incidence i.e., ranging from 0 to 54.10% were observed among these sugarcane cultivars. Besides, pathogen DNA in plant shoots of all the cultivars was successfully amplified by PCR method using smut-specific primers except 26 cultivars which showed an immune reaction in the field trial. Furthermore, the plant germination and tillering of susceptible sugarcane cultivars were greatly influenced by pathogen inoculation. In susceptible cultivars, S. scitamineum caused a significant reduction in setts germination, coupled with profuse tillering, resulting in fewer millable canes. Correlation analysis demonstrated that there was a positive relationship between reduction in setts germination and increase in the number of tillers. The present study would be helpful for the evaluation of smut resistance in a wide range of sugarcane germplasm, especially from the aspects of setts germination and tillers formation, and it also screened out several excellent germplasm for potential application in sugarcane breeding.

Blocking miR396 activity by overexpression MIM396 improved switchgrass tiller number and biomass yield.

BACKGROUND: MicroRNA396 (miR396) plays an important role in the regulation of plant growth and development by repressing the expression level of its target growth-regulating factor (GRF) family genes. In our previous study, we found that overexpression of miR396 negatively regulated both tillering and biomass yield in switchgrass (Panicum virgatum L.). We, therefore, speculated that blocking the expression of miR396 could enhance switchgrass tillering and biomass yield. Here, we produced transgenic switchgrass plants overexpressing a target mimicry form of miR396 (MIM396) in wild type (WT) and Os-MIR319b overexpressing switchgrass plant (with higher enzymatic hydrolysis efficiency, but reduced tillering), in which the expression of miR396 was blocked. The phenotype and biological yields of these plants were analyzed. RESULTS: Blocking miR396 to improve its target PvGRFs expression in switchgrass improved the tiller number and dry weight of transgenic plants. Further morphological analysis revealed that MIM396 plants increased the number of aerial branches and basal tillers compared to those of wild-type plants. The enzymatic efficiency of MIM396 plants was reduced; however, the total sugar production per plant was still significantly higher than that of wild-type plants due to the increase in biomass. In addition, blocking miR396 in a transgenic switchgrass plant overexpressing Os-MIR319b (TG21-Ms) significantly increased the PvGRF1/3/5 expression level and tiller number and biomass yield. The miR156-target gene PvSPL4, playing a negative role in aerial and basal buds outgrowth, showed significant downregulated in MIM396 and TG21-Ms. Those results indicate that miR396-PvGRFs, through disrupting the PvSPL4 expression, are involved in miR319-PvPCFs in regulating tiller number, at least partly. CONCLUSIONS: MIM396 could be used as a molecular tool to improving tiller number and biomass yield in switchgrass wild type and miR319b transgenic plants. This finding may be applied to other graminaceous plants to regulate plant biological yield.

Transcription factor OsSHR2 regulates rice architecture and yield per plant in response to nitrogen.

MAIN CONCLUSION: Mutation of OsSHR2 adversely impacted root and shoot growth and impaired plant response to N conditions, further reducing the yield per plant. Nitrogen (N) is a crucial factor that regulates the plant architecture. There is still a lack of research on it. In our study, it was observed that the knockout of the SHORTROOT 2 (OsSHR2) which was induced by N deficiency, can significantly affect the regulation of plant architecture response to N in rice. Under N deficiency, the mutation of OsSHR2 significantly reduced root growth, and impaired the sensitivity of the root meristem length to N deficiency. The mutants were found to have approximately a 15% reduction in plant height compared to wild type. But mutants showed a significant increase in tillering at post-heading stage, approximately 26% more than the wild type, particularly in high N conditions. In addition, due to reduced seed setting rate and 1000-grain weight, mutant yield was significantly decreased by approximately 33% under low N fertilizer supply. The mutation also changed the distribution of N between the vegetative and reproductive organs. Our findings suggest that the transcription factor OsSHR2 plays a regulatory role in the response of plant architecture and yield per plant to N in rice.

Blocking of amino acid transporter OsAAP7 promoted tillering and yield by determining basic and neutral amino acids accumulation in rice.

BACKGROUND: Amino acids are not only the main form of N in rice, but also are vital for its growth and development. These processes are facilitated by amino acid transporters within the plant. Despite their significance, only a few AAP amino acid transporters have been reported. RESULTS: In this study, we observed that there were differences in the expression of amino acid transporter OsAAP7 among 521 wild cultivated rice varieties, and it directly negatively correlated with tillering and grain yield per plant. We revealed that OsAAP7 protein was localized to the endoplasmic reticulum and had absorption and transport affinity for amino acids such as phenylalanine (Phe), lysine (Lys), leucine (Leu), and arginine (Arg) using subcellular localization, yeast substrate testing, fluorescent amino acid uptake, and amino acid content determination. Further hydroponic studies showed that exogenous application of amino acids Phe, Lys and Arg inhibited the growth of axillary buds in the overexpression lines, and promoted the elongation of axillary buds in the mutant lines. Finally, RNA-seq analysis showed that the expression patterns of genes related to nitrogen, auxin and cytokinin pathways were changed in axillary buds of OsAAP7 transgenic plants. CONCLUSIONS: This study revealed the gene function of OsAAP7, and found that blocking of amino acid transporter OsAAP7 with CRISPR/Cas9 technology promoted tillering and yield by determining basic and neutral amino acids accumulation in rice.

Design, Synthesis and Biological Evaluation of Novel Phenyl-Substituted Naphthoic Acid Ethyl Ester Derivatives as Strigolactone Receptor Inhibitor.

Strigolactones (SLs) are plant hormones that regulate several key agronomic traits, including shoot branching, leaf senescence, and stress tolerance. The artificial regulation of SL biosynthesis and signaling has been considered as a potent strategy in regulating plant architecture and combatting the infection of parasitic weeds to help improve crop yield. DL1b is a previously reported SL receptor inhibitor molecule that significantly promotes shoot branching. Here, we synthesized 18 novel compounds based on the structure of DL1b. We performed rice tillering activity assay and selected a novel small molecule, C6, as a candidate SL receptor inhibitor. In vitro bioassays demonstrated that C6 possesses various regulatory functions as an SL inhibitor, including inhibiting germination of the root parasitic seeds Phelipanche aegyptiaca, delaying leaf senescence and promoting hypocotyl elongation of Arabidopsis. ITC analysis and molecular docking experiments further confirmed that C6 can interact with SL receptor proteins, thereby interfering with the binding of SL to its receptor. Therefore, C6 is considered a novel SL receptor inhibitor with potential applications in plant architecture control and prevention of root parasitic weed infestation.

Physiological and Proteomic Analyses of mtn1 Mutant Reveal Key Players in Centipedegrass Tiller Development.

Tillering directly determines the seed production and propagation capacity of clonal plants. However, the molecular mechanisms involved in the tiller development of clonal plants are still not fully understood. In this study, we conducted a proteome comparison between the tiller buds and stem node of a multiple-tiller mutant mtn1 (more tillering number 1) and a wild type of centipedegrass. The results showed significant increases of 29.03% and 27.89% in the first and secondary tiller numbers, respectively, in the mtn1 mutant compared to the wild type. The photosynthetic rate increased by 31.44%, while the starch, soluble sugar, and sucrose contents in the tiller buds and stem node showed increases of 13.79%, 39.10%, 97.64%, 37.97%, 55.64%, and 7.68%, respectively, compared to the wild type. Two groups comprising 438 and 589 protein species, respectively, were differentially accumulated in the tiller buds and stem node in the mtn1 mutant. Consistent with the physiological characteristics, sucrose and starch metabolism as well as plant hormone signaling were found to be enriched with differentially abundant proteins (DAPs) in the mtn1 mutant. These results revealed that sugars and plant hormones may play important regulatory roles in the tiller development in centipedegrass. These results expanded our understanding of tiller development in clonal plants.

Genome-Wide Association Analysis of Effective Tillers in Rice under Different Nitrogen Gradients.

Nitrogen is a crucial element that impacts rice yields, and effective tillering is a significant agronomic characteristic that can influence rice yields. The way that reduced nitrogen affects effective tillering is a complex quantitative trait that is controlled by multiple genes, and its genetic basis requires further exploration. In this study, 469 germplasm varieties were used for a genome-wide association analysis aiming to detect quantitative trait loci (QTL) associated with effective tillering at low (60 kg/hm2) and high (180 kg/hm2) nitrogen levels. QTLs detected over multiple years or under different treatments were scrutinized in this study, and candidate genes were identified through haplotype analysis and spatio-temporal expression patterns. A total of seven genes (NAL1, OsCKX9, Os01g0690800, Os02g0550300, Os02g0550700, Os04g0615700, and Os04g06163000) were pinpointed in these QTL regions, and were considered the most likely candidate genes. These results provide favorable information for the use of auxiliary marker selection in controlling effective tillering in rice for improved yields.

H2O2 promotes trimming-induced tillering by regulating energy supply and redox status in bermudagrass.

Tillering/branching pattern plays a significant role in determining the structure and diversity of grass, and trimming has been found to induce tillering in turfgrass. Recently, it has been reported that hydrogen peroxide (H2O2) regulates axillary bud development. However, the role of H2O2 in trimming-induced tillering in bermudagrass, a kind of turfgrass, remains unclear. Our study unveils the significant impact of trimming on promoting the sprouting and growth of tiller buds in stolon nodes, along with an increase in the number of tillers in the main stem. This effect is accompanied by spatial-temporal changes in cytokinin and sucrose content, as well as relevant gene expression in axillary buds. In addition, the partial trimming of new-born tillers results in an increase in sucrose and starch reserves in their leaves, which can be attributed to the enhanced photosynthesis capacity. Importantly, trimming promotes a rapid H2O2 burst in the leaves of new-born tillers and axillary stolon buds. Furthermore, exogenous application of H2O2 significantly increases the number of tillers after trimming by affecting the expression of cytokinin-related genes, bolstering photosynthesis potential, energy reserves and antioxidant enzyme activity. Taken together, these results indicate that both endogenous production and exogenous addition of H2O2 enhance the inductive effects of trimming on the tillering process in bermudagrass, thus helping boost energy supply and maintain the redox state in newly formed tillers.

Strigolactone and abscisic acid synthesis and signaling pathways are enhanced in the wheat oligo-tillering mutant ot1.

Tiller number greatly contributes to grain yield in wheat. Using ethylmethanesulfonate mutagenesis, we previously discovered the oligo-tillering mutant ot1. The tiller number was significantly lower in ot1 than in the corresponding wild type from the early tillering stage until the heading stage. Compared to the wild type, the thousand-grain weight and grain length were increased by 15.41% and 31.44%, respectively, whereas the plant height and spike length were decreased by 26.13% and 37.25%, respectively. Transcriptomic analysis was conducted at the regreening and jointing stages to identify differential expressed genes (DEGs). Functional enrichment analysis with the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases showed differential expression of genes associated with ADP binding, transmembrane transport, and transcriptional regulation during tiller development. Differences in tiller number in ot1 led to the upregulation of genes in the strigolactone (SL) and abscisic acid (ABA) pathways. Specifically, the SL biosynthesis genes DWARF (D27), D17, D10, and MORE AXILLARY GROWTH 1 (MAX1) were upregulated by 3.37- to 8.23-fold; the SL signal transduction genes D14 and D53 were upregulated by 1.81- and 1.32-fold, respectively; the ABA biosynthesis genes 9-CIS-EPOXICAROTENOID DIOXIGENASE 3 (NCED3) and NCED5 were upregulated by 1.66- and 3.4-fold, respectively; and SNF1-REGULATED PROTEIN KINASE2 (SnRK2) and PROTEIN PHOSPHATASE 2C (PP2C) genes were upregulated by 1.30- to 4.79-fold. This suggested that the tiller number reduction in ot1 was due to alterations in plant hormone pathways. Genes known to promote tillering growth were upregulated, whereas those known to inhibit tillering growth were downregulated. For example, PIN-FORMED 9 (PIN9), which promotes tiller development, was upregulated by 8.23-fold in ot1; Ideal Plant Architecture 1 (IPA1), which inhibits tiller development, was downregulated by 1.74-fold. There were no significant differences in the expression levels of TILLER NUMBER 1 (TN1) or TEOSINTE BRANCHED 1 (TB1), indicating that the tiller reduction in ot1 was not controlled by known genes. Our findings provide valuable data for subsequent research into the genetic bases and regulatory mechanisms of wheat tillering. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01450-3.

The QTL and Candidate Genes Regulating the Early Tillering Vigor Traits of Late-Season Rice in Double-Cropping Systems.

Rice effective panicle is a major trait for grain yield and is affected by both the genetic tiller numbers and the early tillering vigor (ETV) traits to survive environmental adversities. The mechanism behind tiller bud formation has been well described, while the genes and the molecular mechanism underlying rice-regulating ETV traits are unclear. In this study, the candidate genes in regulating ETV traits have been sought by quantitative trait locus (QTL) mapping and bulk-segregation analysis by resequencing method (BSA-seq) conjoint analysis using rice backcross inbred line (BIL) populations, which were cultivated as late-season rice of double-cropping rice systems. By QTL mapping, seven QTLs were detected on chromosomes 1, 3, 4, and 9, with the logarithm of the odds (LOD) values ranging from 3.52 to 7.57 and explained 3.23% to 12.98% of the observed phenotypic variance. By BSA-seq analysis, seven QTLs on chromosomes 1, 2, 4, 5, 7, and 9 were identified using single-nucleotide polymorphism (SNP) and insertions/deletions (InDel) index algorithm and Euclidean distance (ED) algorithm. The overlapping QTL resulting from QTL mapping and BSA-seq analysis was shown in a 1.39 Mb interval on chromosome 4. In the overlap interval, six genes, including the functional unknown genes Os04g0455650, Os04g0470901, Os04g0500600, and ethylene-insensitive 3 (Os04g0456900), sialyltransferase family domain containing protein (Os04g0506800), and ATOZI1 (Os04g0497300), showed the differential expression between ETV rice lines and late tillering vigor (LTV) rice lines and have a missense base mutation in the genomic DNA sequences of the parents. We speculate that the six genes are the candidate genes regulating the ETV trait in rice, which provides a research basis for revealing the molecular mechanism behind the ETV traits in rice.

Biochemical and Transcriptome Analyses Reveal a Stronger Capacity for Photosynthate Accumulation in Low-Tillering Rice Varieties.

Moderate control of rice tillering and the development of rice varieties with large panicles are important topics for future high-yield rice breeding. Herein, we found that low-tillering rice varieties stopped tillering earlier and had a larger leaf area of the sixth leaf. Notably, at 28 days after sowing, the rice seedlings of the low-tillering group had an average single-culm above-ground biomass of 0.84 g, significantly higher than that of the multi-tillering group by 56.26%, and their NSC (non-structural carbohydrate) and starch contents in sheaths were increased by 43.34% and 97.75%, respectively. These results indicated that the low-tillering group of rice varieties had a stronger ability to store photosynthetic products in the form of starch in their sheaths, which was thus more beneficial for their large panicle development. The results of carbon and nitrogen metabolism analyses showed that the low-tillering group had a relatively strong carbon metabolism activity, which was more favorable for the accumulation of photosynthesis products and the following development of large panicles, while the multi-tillering group showed relatively strong nitrogen metabolism activity, which was more beneficial for the development and formation of new organs, such as tillers. Accordingly, in the low-tillering rice varieties, the up-regulated genes were enriched in the pathways mainly related to the synthesis of carbohydrates, while the down-regulated genes were mainly enriched in the nitrogen metabolism pathways. This study provides new insights into the mechanism of rice tillering regulation and promotes the development of new varieties with ideal plant types.

A chromosome arm from Thinopyrum intermedium × Thinopyrum ponticum hybrid confers increased tillering and yield potential in wheat.

Tiller number is a key component of wheat plant architecture having a direct impact on grain yield. Because of their viability, biotic resistance, and abiotic stress tolerance, wild relative species are a valuable gene source for increasing wheat genetic diversity, including yield potential. Agropyron glael, a perennial hybrid of Thinopyrum intermedium and Th. ponticum, was created in the 1930s. Recent genome analyses identified five evolutionarily distinct subgenomes (J, Jst, Jvs, Jr, and St), making A. glael an important gene source for transferring useful agronomical traits into wheat. During a bread wheat × A. glael crossing program, a genetically stable translocation line, WT153397, was developed. Sequential in situ hybridizations (McGISH) with J-, St-, and D-genomic DNA probes and pSc119.2, Afa family, pTa71, and (GAA)7 DNA repeats, as well as molecular markers specific for the wheat 6D chromosome, revealed the presence of a 6DS.6Jvs Robertsonian translocation in the genetic line. Field trials in low-input and high-input breeding nurseries over four growing seasons demonstrated the Agropyron chromosome arm's high compensating ability for the missing 6DL, as spike morphology and fertility of WT153397 did not differ significantly from those of wheat parents, Mv9kr1 and 'Mv Karizma.' Moreover, the introgressed 6Jvs chromosome arm significantly increased the number of productive tillers, resulting in a significantly higher grain yield potential compared to the parental wheat cultivars. The translocated chromosome could be highly purified by flow cytometric sorting due to the intense fluorescent labeling of (GAA)7 clusters on the Thinopyrum chromosome arm, providing an opportunity to use chromosome genomics to identify Agropyron gene variant(s) responsible for the tillering capacity. The translocation line WT153397 is an important genetic stock for functional genetic studies of tiller formation and useful breeding material for increasing wheat yield potential. The study also discusses the use of the translocation line in wheat breeding. Supplementary information: The online version contains supplementary material available at 10.1007/s11032-024-01439-y.

Wheat ESCRT-III protein TaSAL1 regulates male gametophyte transmission and controls tillering and heading date.

Charged multivesicular protein 1 (CHMP1) is a member of the endosomal sorting complex required for transport-III (ESCRT-III) complex that targets membrane localized signaling receptors to intralumenal vesicles in the multivesicular body of the endosome and eventually to the lysosome for degradation. Although CHMP1 plays roles in various plant growth and development processes, little is known about its function in wheat. In this study, we systematically analysed the members of the ESCRT-III complex in wheat (Triticum aestivum) and found that their orthologs were highly conserved in eukaryotic evolution. We identified CHMP1 homologous genes, TaSAL1s, and found that they were constitutively expressed in wheat tissues and essential for plant reproduction. Subcellular localization assays showed these proteins aggregated with and closely associated with the endoplasmic reticulum when ectopically expressed in tobacco leaves. We also found these proteins were toxic and caused leaf death. A genetic and reciprocal cross analysis revealed that TaSAL1 leads to defects in male gametophyte biogenesis. Moreover, phenotypic and metabolomic analysis showed that TaSAL1 may regulate tillering and heading date through phytohormone pathways. Overall, our results highlight the role of CHMP1 in wheat, particularly in male gametophyte biogenesis, with implications for improving plant growth and developing new strategies for plant breeding and genetic engineering.