Rice Plant Architecture Research Articles

Understanding abscisic acid-mediated stress signaling to affect rice development under stress

IntroductionRice is a vital staple food for many countries, and its yield is known to be significantly affected by various abiotic stresses, which are expected to intensify with climate change, posing a threat to global food security. Abscisic acid (ABA), a crucial plant growth regulator, plays a crucial role in plant responses to these abiotic stresses. It influences several processes, such as seed dormancy, leaf gas exchange, reactive oxygen species (ROS) scavenging, ion toxicity reduction, and root elongation, all of which contribute to enhancing plant survival under stress.MethodsThis article reviews recent research on ABA-mediated gene responses and expressions involved in rice plant architecture and its response to abiotic stress.Results and discussionAbscisic acid responses were primarily driven by changes in gene expression. Expression analyses of the gene related to ABA biosynthesis or catabolism indicated several changes in plant architecture, such as changes in leaf angle, delayed flowering, and modifications in growth regulators. Additionally, tolerance-related mechanisms, such as increased ROS scavenging, reduced membrane leakage, and vacuolar compartmentation of toxic radicals, were activated under single or multiple stress conditions. While these adaptations may improve plant survival and yield sustainability under stress, they may not necessarily enhance yield potential in environments affected by drought, salinity, or heat stress. ABA expression was also associated with improved pollen viability, grain-filling potential, and seed setting under abiotic stresses such as heat, which could enhance seed yield in such challenging environments.

NADP-malic Enzyme OsNADP-ME2 Modulates Plant Height Involving in Gibberellin Signaling in Rice

Plants NADP-malic enzymes (NADP-MEs) act as a class of oxidative decarboxylase to mediate malic acid metabolism in organisms. Despite NADP-MEs have been demonstrated to play pivotal roles in regulating diverse biological processes, the role of NADP-MEs involving in plant growth and development remains rarely known. Here, we characterized the function of rice cytosolic OsNADP-ME2 in regulating plant height. The results showed that RNAi silencing and knock-out of OsNADP-ME2 in rice results in a dwarf plant structure, associating with significant expression inhibition of genes involving in phytohormone Gibberellin (GA) biosynthesis and signaling transduction, but with up-regulation for the expression of GA signaling suppressor SLR1. The accumulation of major bioactive GA1, GA4 and GA7 are evidently altered in RNAi lines, and exogenous GA treatment compromises the dwarf phenotype of OsNADP-ME2 RNAi lines. RNAi silencing of OsNADP-ME2 also causes the reduction of NADP-ME activity associating with decreased production of pyruvate. Thus, our data revealed a novel function of plant NADP-MEs in modulation of rice plant height through regulating bioactive GAs accumulation and GA signaling, and provided a valuable gene resource for rice plant architecture improvement.

LATA1, a RING E3 ligase, modulates the tiller angle by affecting auxin asymmetric distribution and content in rice.

The tiller angle is an important agronomic trait that determines plant architecture and grain yield in rice (Oryza sativa L.). However, the molecular regulation mechanism of the rice tiller angle remains unclear. Here, we identified a rice tiller angle gene, LARGE TILLER ANGLE 1 (LATA1), using the MutMap approach. LATA1 encodes a C3H2C3-type RING zinc finger E3 ligase and the conserved region of the RING zinc finger is essential for its E3 activity. LATA1 was highly expressed in the root and tiller base and LATA1-GFP fusion protein was specifically localized to the nucleus. The mutation of LATA1 significantly reduced indole-3-acetic acid content and attenuated lateral auxin transport, thereby resulting in defective shoot gravitropism and spreading plant architecture in rice. Further investigations found that LATA1 may indirectly affect gravity perception by modulating the sedimentation rate of gravity-sensing amyloplasts upon gravistimulation. Our findings provide new insights into the molecular mechanism underlying the rice tiller angle and new genetic resource for the improvement of plant architecture in rice.

Identification and Fine Mapping of Quantitative Trait Loci for Tiller Angle Using Chromosome Segment Substitution Lines in Rice (Oryza Sativa L.)

The tiller angle, which is an important agronomic trait, determines plant architecture and greatly influences the grain yield of rice. In this study, a population of chromosome segment substitution lines derived from a cross between a japonica variety with a compact plant architecture—Koshihikari—and an indica variety with a spread-out plant architecture—Nona Bokra—was used to investigate the genetic basis of the tiller angle. Five quantitative trait loci (qTA1, qTA5, qTA9-1, qTA9-2, and qTA11) for the tiller angle were detected on chromosomes 1, 5, 9, 9, and 11 in two different environments. The phenotypic variation in these QTLs ranged from 3.78% to 8.22%. Two pairs of digenic epistatic QTLs were detected in Lingshui. The epistatic interaction explained 15.19% and 13.60% of the phenotypic variance, respectively. Among the five QTLs, qTA9-2 was detected in both environments. An F2 mapping population containing the qTA9-2 QTL was established. The location of qTA9-2 was narrowed down to a 187 kb region between InDel markers M9 and M10 on chromosome 9. Thirty open reading frames (ORFs), including TAC1, a gene known to regulate the tiller angle, were identified in this region. The gene sequencing results suggested that a base substitution from G to A at position 1557 in the 3′-untranslated region led to a difference in the expression of qTA9-2 in Koshihikari and Nona Bokra. These findings provide a potential gene resource for the improvement of rice plant architecture.

Ectopic expression of OsWOX9A alters leaf anatomy and plant architecture in rice.

Ectopic expression of OsWOX9A induces narrow adaxially rolled rice leaves with larger bulliform cells and fewer large veins, probably through regulating the expression of auxin-related and expansin genes. The WUSCHEL-related homeobox (WOX) family plays a pivotal role in plant development by regulating genes involved in various aspects of growth and differentiation. OsWOX9A (DWT1) has been linked to tiller growth, uniform plant growth, and flower meristem activity. However, its impact on leaf growth and development in rice has not been studied. In this study, we investigated the biological role of OsWOX9A in rice growth and development using transgenic plants. Overexpression of OsWOX9A conferred narrow adaxially rolled rice leaves and altered plant architecture. These plants exhibited larger bulliform cells and fewer larger veins compared to wild-type plants. OsWOX9A overexpression also reduced plant height, tiller number, and seed-setting rate. Comparative transcriptome analysis revealed several differentially expressed auxin-related and expansin genes in OsWOX9A overexpressing plants, consistent with their roles in leaf and plant development. These results indicate that the ectopic expression of OsWOX9A may have multiple effects on the development and growth of rice, providing a more comprehensive picture of how the WOX9 subfamily contributes to leaf development and plant architecture.

The BEL1-like homeodomain protein OsBLH4 regulates rice plant height, grain number, and heading date by repressing the expression of OsGA2ox1.

Gibberellins (GAs) play crucial roles in regulating plant architecture and grain yield of crops. In rice, the inactivation of endogenous bioactive GAs and their precursors by GA 2-oxidases (GA2oxs) regulates stem elongation and reproductive development. However, the regulatory mechanisms of GA2ox gene expression, especially in rice reproductive organs, are unknown. The BEL1-like homeodomain protein OsBLH4, a negative regulatory factor for the rice OsGA2ox1 gene, was identified in this study. Loss of OsBLH4 function results in decreased bioactive GA levels and pleiotropic phenotypes, including reduced plant height, decreased grain number per panicle, and delayed heading date, as also observed in OsGA2ox1-overexpressing plants. Consistent with the mutant phenotype, OsBLH4 was predominantly expressed in shoots and young spikelets; its encoded protein was exclusively localized in the nucleus. Molecular analysis demonstrated that OsBLH4 directly bound to the promoter region of OsGA2ox1 to repress its expression. Genetic assays revealed that OsBLH4 acts upstream of OsGA2ox1 to control rice plant height, grain number, and heading date. Taken together, these results indicate a crucial role for OsBLH4 in regulating rice plant architecture and yield potential via regulation of bioactive GA levels, and provide a potential strategy for genetic improvements of rice.

Combining modeling and experimental approaches for developing rice-oil palm agroforestry systems.

Monoculture systems in South East Asia are facing challenges due to climate change-induced extreme weather conditions, leading to significant annual production losses in rice and oil palm. To ensure the stability of these crops, innovative strategies like resilient agroforestry systems need to be explored. Converting oil palm (Elaeis guineensis) monocultures to rice (Oryza sativa)-based intercropping systems shows promise, but achieving optimal yields requires adjusting palm density and identifying rice varieties adapted to changes in light quantity and diurnal fluctuation. This paper proposes a methodology that combines a model of light interception with indoor experiments to assess the feasibility of rice-oil palm agroforestry systems. Using a functional-structural plant model of oil palm, the planting design was optimized to maximize transmitted light for rice. Simulation results estimated the potential impact on oil palm carbon assimilation and transpiration. In growth chambers, simulated light conditions were replicated with adjustments to intensity and daily fluctuation. Three light treatments independently evaluated the effects of light intensity and fluctuation on different rice accessions. The simulation study revealed intercropping designs that significantly increased light transmission for rice cultivation with minimal decrease in oil palm densities compared with conventional designs. The results estimated a loss in oil palm productivity of less than 10%, attributed to improved carbon assimilation and water use efficiency. Changes in rice plant architecture were primarily influenced by light quantity, while variations in yield components were attributed to light fluctuations. Different rice accessions exhibited diverse responses to light fluctuations, indicating the potential for selecting genotypes suitable for agroforestry systems.

DNAL7, a new allele of NAL11, has major pleiotropic effects on rice architecture.

dnal7, a novel allelic variant of the OsHSP40, affects rice plant architecture and grain yield by coordinating auxins, cytokinins, and gibberellic acids. Plant height and leaf morphology are the most important traits of the ideal plant architecture (IPA), and discovering related genes is critical for breeding high-yield rice. Here, a dwarf and narrow leaf 7 (dnal7) mutant was identified from a γ-ray treated mutant population, which exhibits pleiotropic effects, including dwarfing, narrow leaves, small seeds, and low grain yield per plant compared to the wild type (WT). Histological analysis showed that the number of veins and the distance between adjacent small veins (SVs) were significantly reduced compared to the WT, indicating that DNAL7 controls leaf size by regulating the formation of veins. Map-based cloning and transgenic complementation revealed that DNAL7 is allelic to NAL11, which encodes OsHSP40, and the deletion of 2 codons in dnal7 destroyed the His-Pro-Asp (HPD) motif of OsHSP40. In addition, expression of DNAL7 in both WT and dnal7 gradually increased with the increase of temperature in the range of 27-31°C. Heat stress significantly affected the seedling height and leaf width of the dnal7 mutant. A comparative transcriptome analysis of WT and dnal7 revealed that DNAL7 influenced multiple metabolic pathways, including plant hormone signal transduction, carbon metabolism, and biosynthesis of amino acids. Furthermore, the contents of the cytokinins in leaf blades were much higher in dnal7 than in the WT, whereas the contents of auxins were lower in dnal7. The contents of bioactive gibberellic acids (GAs) including GA1, GA3, and GA4 in shoots were decreased in dnal7. Thus, DNAL7 regulates rice plant architecture by coordinating the balance of auxins, cytokinins, and GAs. These results indicate that OsHSP40 is a pleiotropic gene, which plays an important role in improving rice yield and plant architecture.

OsNAC103, a NAC Transcription Factor, Positively Regulates Leaf Senescence and Plant Architecture in Rice

Leaf senescence, the last stage of leaf development, is essential for crop yield by promoting nutrition relocation from senescence leaves to new leaves and seeds. NAC (NAM/ATAF1/ATAF2/CUC2) proteins, one of the plant-specific transcription factors, widely distribute in plants and play important roles in plant growth and development. Here, we identified a new NAC member OsNAC103 and found that it plays critical roles in leaf senescence and plant architecture in rice. OsNAC103 mRNA levels were dramatically induced by leaf senescence as well as different phytohormones such as ABA, MeJA and ACC and abiotic stresses including dark, drought and high salinity. OsNAC103 acts as a transcription factor with nuclear localization signals at the N terminal and a transcriptional activation signal at the C terminal. Overexpression of OsNAC103 promoted leaf senescence while osnac103 mutants delayed leaf senescence under natural condition and dark-induced condition, meanwhile, senescence-associated genes (SAGs) were up-regulated in OsNAC103 overexpression (OsNAC103-OE) lines, indicating that OsNAC103 positively regulates leaf senescence in rice. Moreover, OsNAC103-OE lines exhibited loose plant architecture with larger tiller angles while tiller angles of osnac103 mutants decreased during the vegetative and reproductive growth stages due to the response of shoot gravitropism, suggesting that OsNAC103 can regulate the plant architecture in rice. Taken together, our results reveal that OsNAC103 plays crucial roles in the regulation of leaf senescence and plant architecture in rice.

SMALL PLANT AND ORGAN 1 (SPO1) Encoding a Cellulose Synthase-like Protein D4 (OsCSLD4) Is an Important Regulator for Plant Architecture and Organ Size in Rice

Plant architecture and organ size are considered as important traits in crop breeding and germplasm improvement. Although several factors affecting plant architecture and organ size have been identified in rice, the genetic and regulatory mechanisms remain to be elucidated. Here, we identified and characterized the small plant and organ 1 (spo1) mutant in rice (Oryza sativa), which exhibits narrow and rolled leaf, reductions in plant height, root length, and grain width, and other morphological defects. Map-based cloning revealed that SPO1 is allelic with OsCSLD4, a gene encoding the cellulose synthase-like protein D4, and is highly expressed in the roots at the seedling and tillering stages. Microscopic observation revealed the spo1 mutant had reduced number and width in leaf veins, smaller size of leaf bulliform cells, reduced cell length and cell area in the culm, and decreased width of epidermal cells in the outer glume of the grain. These results indicate the role of SPO1 in modulating cell division and cell expansion, which modulates plant architecture and organ size. It is showed that the contents of endogenous hormones including auxin, abscisic acid, gibberellin, and zeatin tested in the spo1 mutant were significantly altered, compared to the wild type. Furthermore, the transcriptome analysis revealed that the differentially expressed genes (DEGs) are significantly enriched in the pathways associated with plant hormone signal transduction, cell cycle progression, and cell wall formation. These results indicated that the loss of SPO1/OsCSLD4 function disrupted cell wall cellulose synthase and hormones homeostasis and signaling, thus leading to smaller plant and organ size in spo1. Taken together, we suggest the functional role of SPO1/OsCSLD4 in the control of rice plant and organ size by modulating cell division and expansion, likely through the effects of multiple hormonal pathways on cell wall formation.

Genotype‐by‐environmental interaction effects on earliness, semi‐dwarfism, and yield of rice (Oryza sativa L.) mutants in Tamil Nadu, India

AbstractRice plant architecture improvement helps in the effective and efficient source–sink relationship to enhance yield. The most preferred plant architecture in rice is dwarf type. Improved White Ponni (IWP) is a tall, medium duration, released variety of Tamil Nadu, India, yielding 300 kg more than parental line White Ponni, which is suitable for second season transplanting. To induce variation in plant height to select semi‐dwarf mutants, IWP was subjected to mutagenesis in 2011 using different doses of gamma rays to develop semi‐dwarf and short‐duration mutants. The selection was carried out in segregating populations of M2, and an evaluation of selected better‐performing mutants was done up to 70 selected mutants in M5. Nineteen M5 homozygous, semi‐dwarf, and short‐duration mutants that outperformed the IWP were evaluated in 2015–2016 across five contrasting environments of Tamil Nadu in India. The genotypes were grown in a randomized complete block design with two replications with IWP as a control. In the additive main effects and multiplicative interaction (AMMI) biplot, the analysis revealed that PC1 and PC2 accounted for 49% and 18% of the variation, respectively. Interaction principal component analysis‐1 scores were observed for the mutants, viz., IWP‐15‐5, IWP‐22‐1, and IWP‐30‐5, indicating their superior performance. In the GGE biplot, E1 (Aduthurai), E4 (Coimbatore), and E5 (Thirupathisaram) were the ideal environments for selecting high‐yielding mutants. IWP‐6‐5 and IWP‐16‐2 were the stable mutants for yield (23.59 and 24.51 g, respectively) but with a lower mean than other mutants at favorable environments. Based on the two models, E2 (Killikulam) and E3 (Madurai) were the favorable locations for exploiting high yields; IWP‐30‐5, IWP‐22‐2, and IWP‐22‐3 were stable across environments. These stable, high‐yielding, and early maturing mutants show potential for further advancement and eventual release of new rice varieties.

QGLF5 from Oryza rufipogon Griff. improves kernel shape, plant architecture, and yield in rice.

A novel QTL qGLF5 from Oryza rufipogon Griff. improves yield per plant and plant architecture in rice. Kernel size and plant architecture are critical agronomic traits that are key targets for improving crop yield. From the single-segment substitution lines of Oryza rufipogon Griff. in the indica cultivar Huajingxian74 (HJX74) background, we identified a novel quantitative trait locus (QTL), named qGLF5, which improves kernel shape, plant architecture, and yield per plant in rice. Compared with the control HJX74, the plant height, panicles per plant, panicle length, primary branches per panicle, secondary branches per panicle, and kernels per plant of the near-isogenic line-qGLF5 (NIL-qGLF5) are significantly increased. NIL-qGLF5 has long and narrow kernels by regulating cell number, cell length and width in the spikelet hulls. Yield per plant of NIL-qGLF5 is increased by 35.02% compared with that of HJX74. In addition, qGLF5 significantly improves yield per plant and plant architecture of NIL-gw5 and NIL-GW7. These results indicate that qGLF5 might be beneficial for improving plant architecture and kernel yield in rice breeding by molecular design.

A Structure Variation in qPH8.2 Detrimentally Affects Plant Architecture and Yield in Rice.

Plant height is an important agronomic trait associated with plant architecture and grain yield in rice (Oryza sativa L.). In this study, we report the identification of quantitative trait loci (QTL) for plant height using a chromosomal segment substitution line (CSSL) population with substituted segments from japonica variety Nipponbare (NIP) in the background of the indica variety 9311. Eight stable QTLs for plant height were identified in three environments. Among them, six loci were co-localized with known genes such as semidwarf-1 (sd1) and Grain Number per Panicle1 (GNP1) involved in gibberellin biosynthesis. A minor QTL qPH8.2 on chromosome 8 was verified and fine-mapped to a 74 kb region. Sequence comparison of the genomic region revealed the presence/absence of a 42 kb insertion between NIP and 9311. This insertion occurred predominantly in temperate japonica rice. Comparisons on the near-isogenic lines showed that the qPH8.2 allele from NIP exhibits pleiotropic effects on plant growth, including reduced plant height, leaf length, photosynthetic capacity, delayed heading date, decreased yield, and increased tiller angle. These results indicate that qPH8.2 from temperate japonica triggers adverse effects on plant growth and yield when introduced into the indica rice, highlighting the importance of the inter-subspecies crossing breeding programs.

QGL3.4 controls kernel size and plant architecture in rice.

Kernel size and plant architecture play important roles in kernel yield in rice. Cloning and functional study of genes related to kernel size and plant architecture are of great significance for breeding high-yield rice. Using the single-segment substitution lines which developed with Oryza barthii as a donor parent and an elite indica cultivar Huajingxian74 (HJX74) as a recipient parent, we identified a novel QTL (quantitative trait locus), named qGL3.4, which controls kernel size and plant architecture. Compared with HJX74, the kernel length, kernel width, 1000-kernel weight, panicle length, kernels per plant, primary branches, yield per plant, and plant height of near isogenic line-qGL3.4 (NIL-qGL3.4) are increased, whereas the panicles per plant and secondary branches per panicle of NIL-qGL3.4 are comparable to those of HJX74. qGL3.4 was narrowed to a 239.18 kb interval on chromosome 3. Cell analysis showed that NIL-qGL3.4 controlled kernel size by regulating cell growth. qGL3.4 controls kernel size at least in part through regulating the transcription levels of EXPANSINS, GS3, GL3.1, PGL1, GL7, OsSPL13 and GS5. These results indicate that qGL3.4 might be beneficial for improving kernel yield and plant architecture in rice breeding.

DWARF AND LOW-TILLERING 2 functions in brassinosteroid signaling and controls plant architecture and grain size in rice.

Brassinosteroids (BRs) are a class of steroid phytohormones that control various aspects of plant growth and development. Several transcriptional factors (TFs) have been suggested to play roles in BR signaling. However, their possible relationship remains largely unknown. Here, we identified a rice mutant dwarf and low-tillering 2 (dlt2) with altered plant architecture, increased grain width, and reduced BR sensitivity. DLT2 encodes a GIBBERELLIN INSENSITIVE (GAI)-REPRESSOR OF GAI (RGA)-SCARECROW (GRAS) TF that is mainly localized in the nucleus and has weak transcriptional activity. Our further genetic and biochemical analyses indicate that DLT2 interacts with two BR-signaling-related TFs, DLT and BRASSINAZOLE-RESISTANT 1, and probably modulates their transcriptional activity. These findings imply that DLT2 is implicated in a potentially transcriptional complex that mediates BR signaling and rice development and suggests that DLT2 could be a potential target for improving rice architecture and grain morphology. This work also sheds light on the role of rice GRAS members in regulating numerous developmental processes.

Curling Leaf 1, Encoding a MYB-Domain Protein, Regulates Leaf Morphology and Affects Plant Yield in Rice.

The leaf is the main site of photosynthesis and is an important component in shaping the ideal rice plant architecture. Research on leaf morphology and development will lay the foundation for high-yield rice breeding. In this study, we isolated and identified a novel curling leaf mutant, designated curling leaf 1 (cl1). The cl1 mutant exhibited an inward curling phenotype because of the defective development of sclerenchymatous cells on the abaxial side. Meanwhile, the cl1 mutant showed significant reductions in grain yield and thousand-grain weight due to abnormal leaf development. Through map-based cloning, we identified the CL1 gene, which encodes a MYB transcription factor that is highly expressed in leaves. Subcellular localization studies confirmed its typical nuclear localization. Transcriptome analysis revealed a significant differential expression of the genes involved in photosynthesis, leaf morphology, yield formation, and hormone metabolism in the cl1 mutant. Yeast two-hybrid assays demonstrated that CL1 interacts with alpha-tubulin protein SRS5 and AP2/ERF protein MFS. These findings provide theoretical foundations for further elucidating the mechanisms of CL1 in regulating leaf morphology and offer genetic resources for practical applications in high-yield rice breeding.

Overexpression of OsPIN9 Impairs Chilling Tolerance via Disturbing ROS Homeostasis in Rice.

The auxin efflux transporter PIN-FORMED (PIN) family is one of the major protein families that facilitates polar auxin transport in plants. Here, we report that overexpression of OsPIN9 leads to altered plant architecture and chilling tolerance in rice. The expression profile analysis indicated that OsPIN9 was gradually suppressed by chilling stress. The shoot height and adventitious root number of OsPIN9-overexpressing (OE) plants were significantly reduced at the seedling stage. The roots of OE plants were more tolerant to N-1-naphthylphthalamic acid (NPA) treatment than WT plants, indicating the disturbance of auxin homeostasis in OE lines. The chilling tolerance assay showed that the survival rate of OE plants was markedly lower than that of wild-type (WT) plants. Consistently, more dead cells, increased electrolyte leakage, and increased malondialdehyde (MDA) content were observed in OE plants compared to those in WT plants under chilling conditions. Notably, OE plants accumulated more hydrogen peroxide (H2O2) and less superoxide anion radicals (O2-) than WT plants under chilling conditions. In contrast, catalase (CAT) and superoxide dismutase (SOD) activities in OE lines decreased significantly compared to those in WT plants at the early chilling stage, implying that the impaired chilling tolerance of transgenic plants is probably attributed to the sharp induction of H2O2 and the delayed induction of antioxidant enzyme activities at this stage. In addition, several OsRboh genes, which play a crucial role in ROS production under abiotic stress, showed an obvious increase after chilling stress in OE plants compared to that in WT plants, which probably at least in part contributes to the production of ROS under chilling stress in OE plants. Together, our results reveal that OsPIN9 plays a vital role in regulating plant architecture and, more importantly, is involved in regulating rice chilling tolerance by influencing auxin and ROS homeostasis.

GS6.1 controls kernel size and plant architecture in rice.

A novel QTL GS6.1 increases yield per plant by controlling kernel size, plant architecture, and kernel filling in rice. Kernel size and plant architecture are critical agronomic traits that greatly influence kernel yield in rice. Using the single-segment substitution lines (SSSLs) with an indica cultivar Huajingxian74 as a recipient parent and American Jasmine as a donor parent, we identified a novel quantitative trait locus (QTL), named GS6.1. Near isogenic line-GS6.1 (NIL-GS6.1) produces long and narrow kernels by regulating cell length and width in the spikelet hulls, thus increasing the 1000-kernel weight. Compared with the control, the plant height, panicles per plant, panicle length, kernels per plant, secondary branches per panicle, and yield per plant of NIL-GS6.1 are increased. In addition, GS6.1 regulates the kernel filling rate. GS6.1 controls kernel size by modulating the transcription levels of part of EXPANSINs, kernel filling-related genes, and kernel size-related genes. These results indicate that GS6.1 might be beneficial for improving kernel yield and plant architecture in rice breeding by molecular design.

Photoperiod and gravistimulation-associated Tiller Angle Control 1 modulates dynamic changes in rice plant architecture.

TAC1 is involved in photoperiodic and gravitropic responses to modulate rice dynamic plant architecture likely by affecting endogenous auxin distribution, which could explain TAC1 widespread distribution in indica rice. Plants experience a changing environment throughout their growth, which requires dynamic adjustments of plant architecture in response to these environmental cues. Our previous study demonstrated that Tiller Angle Control 1 (TAC1) modulates dynamic changes in plant architecture in rice; however, the underlying regulatory mechanisms remain largely unknown. In this study, we show that TAC1 regulates plant architecture in an expression dose-dependent manner, is highly expressed in stems, and exhibits dynamic expression in tiller bases during the growth period. Photoperiodic treatments revealed that TAC1 expression shows circadian rhythm and is more abundant during the dark period than during the light period and under short-day conditions than under long-day conditions. Therefore, it contributes to dynamic plant architecture under long-day conditions and loose plant architecture under short-day conditions. Gravity treatments showed that TAC1 is induced by gravistimulation and negatively regulates shoot gravitropism, likely by affecting auxin distribution. Notably, the tested indica rice containing TAC1 displayed dynamic plant architecture under natural long-day conditions, likely explaining the widespread distribution of TAC1 in indica rice. Our results provide new insights into TAC1-mediated regulatory mechanisms for dynamic changes in rice plant architecture.

Mutation of DEP1 facilitates the improvement of plant architecture in Xian rice (Oryza sativa)

AbstractPlant architecture is a complex trait and has a profound impact on crop performance and productivity. We applied the CRISPR/Cas9 system to mutate the DEP1 gene, which has been reported to function as regulator of plant architecture, in elite Xian cultivar ‘Huhan1509’. Sequencing analysis of T0 transformed plants showed that the CRISPR/Cas9 system was highly efficient in mutagenesis of targeted DEP1 gene, with 30% of the homozygous mutations and 70% of the heterozygous mutations. T2 homozygous mutants without T‐DNA were further examined for the agronomic traits. The DEP1 mutants exhibited an altered plant architecture along with a shorter plant height and grain size and increased spikelets and grain density. Furthermore, phenotypes of raising primary branches and stem diameters were observed in the DEP1 mutants. Our results demonstrate that favourable alleles of the DEP1 gene, developed by CRISPR/Cas9 system, could be used to improve plant architecture in Xian rice.