Tillering architecture directly impacts crop yield, yet the precise regulatory networks governing high-order tiller development remain largely undefined. Here, we report that the HD-ZIP III transcription factor LF1 orchestrates high-order tillering in rice. Evasion of miRNA165/166-mediated repression leads to the ectopic expression of LF1, which triggers excessive high-order tiller outgrowth. Mechanistically, LF1 forms a negative feedback loop with the core tillering regulator MOC1, wherein LF1 directly activates MOC1 transcription and enhances its protein stability to promote axillary meristem initiation, while MOC1 reciprocally triggers LF1 degradation. Concurrently, LF1 directly activates the strigolactone (SL) biosynthesis genes D10 and D27, functioning as a hormonal brake to prevent excessive tiller bud elongation. Furthermore, natural variations in the LF1 promoter strongly correlate with indica-japonica tillering differentiation. Together, our findings elucidate a homeostatic network integrating transcriptional regulation, protein stability, and hormone signaling to shape plant architecture.

Leaf angle is a key determinant of plant architecture and grain yield in rice, yet the complex genetic regulatory network remains unclear. Here, we reveal that the HD-ZIP III transcription factor LF1 mediates brassinosteroid (BR) signaling to modulate leaf angle. A miRNA165/166-resistant, gain-of-function lf1 mutant displays an enlarged leaf angle driven by elongated adaxial parenchymal cells and diminished abaxial sclerenchyma. At the transcriptional level, the BR-activated transcription factor OsBZR1 directly induces LF1, which in turn upregulates OsOFP8, forming an OsBZR1-LF1-OsOFP8 hierarchical transcriptional cascade that mediates BR signaling to regulate leaf angle development. At the post-translational level, LF1 protein stability is fine-tuned by reciprocal post-translational modifications, wherein OsMAPK6-mediated phosphorylation at threonine residue at position 148 promotes LF1 accumulation and transcriptional activity, directly counteracting its ubiquitination and degradation by the APC/CTAD1 complex. Genetic analyses demonstrate that LF1, OsMAPK6, and TAD1 function in a common pathway to regulate leaf angle development. Overall, our study establishes LF1 as a central hub coupling transcriptional and post-translational mechanisms to modulate BR-mediated leaf angle, providing targets for plant architecture improvement.

As the outermost floral organ of the rice spikelet, the normal morphological development of the glume (lemma and palea) is fundamental to grain morphology, quality, and yield formation. However, the regulatory mechanisms governing rice lemma development remain incompletely understood. Here, we identified a rice mutant, drb4, which is defective in lemma polarity development and displays abnormal phenotypes including narrowed or filamentous lemmas. DRB4 is highly expressed in floral organs. It encodes a double-stranded RNA-binding protein containing three DSRM domains and localizes to both the cytoplasm and nucleus. In drb4, the synthesis of ta-siRNA, particularly tasiR-ARF, is significantly reduced, leading to the ectopic expression of their downstream target genes OsARFs on the adaxial of the lemma. Furthermore, biochemical and genetic evidence indicates that DRB4 interacts with OsDCL4 and jointly participates in the biosynthesis of tasiR-ARF. Eventually, it regulates the polarity development of the glume, especially the development of the lemma, by influencing the polarity expression of OsARFs in the glume. Our findings established a crucial DRB4-OsDCL4-tasiR-ARF-OsARF module that precisely controls rice lemma polarity, providing new insights into floral organ development.

Plant mechanical strength affects lodging resistance and stress tolerance, highlighting the importance of elucidating the regulatory mechanisms underlying cell wall development. In this study, we identified a novel dwarf and brittle culm mutant, dbc3, which exhibited reduced culm mechanical strength due to a thinner secondary cell wall, irregular distribution of the sclerenchyma cells under the epidermal layer and vascular bundle cells, as well as a significant reduction in cellulose and lignin content. Map-based cloning revealed that DBC3 encodes a xylan arabinosyltransferase belonging to the GT61 family. GUS staining and qRT-PCR showed that DBC3 was expressed in all tested tissues. Yeast one-hybrid, dual-luciferase assays and EMSA demonstrated that OsMYB63 directly bound to the DBC3 promoter to activate its expression. In the osmyb63 knockout mutant, DBC3 expression was significantly reduced, accompanied by a moderate decrease in stem mechanical strength. Taken together, these findings suggest that DBC3, as a direct target gene of OsMYB63, plays an important role in regulating plant mechanical strength by modulating cell wall development.

Grain size is a pivotal factor that significantly influences grain yield. However, the genetic basis is mostly unknown. Here, we found that our previously identified wl1 mutant, which regulates leaf width development through the APC/CTAD1-WL1-NAL1 pathway, also exhibits a wide grain phenotype with increased cell expansion and proliferation in glume. Genetic analysis showed that the APC/CTAD1-WL1 module also regulates grain width in a common pathway. Further, WL1 can bind to the regulatory regions of Narrow Leaf 2 (NAL2) (a grain width positive regulatory gene) directly to repress its expression by downregulating histone acetylation levels of the chromatin to regulate grain width development. Meanwhile, we also found that WL1 participates in the cytokinin signaling pathway and regulates grain width by interacting with cytokinin B-type response regulator RRB2 and inhibiting its transcriptional activation activity on A-type response regulator OsRR6. In summary, this study established a pivotal WL1-mediated grain size regulation pathway, which is crucial for understanding grain development and improving crop yield.

>Aerial organs in rice, including leaves, stems, and grains, are crucial for photosynthesis, lodging resistance, and yield.Therefore, an in-depth study on the development of these organs can lay a foundation for achieving high and stable rice yields.

Sucrose (Suc) is transported from source leaves to sink tissues to sustain plant growth, development, and crop yield. However, the molecular mechanisms underlying carbohydrate partitioning still remain largely unclear. Here, we report a rice (Oryza sativa) mutant aberrant carbohydrate partitioning 1 (acp1), which hyperaccumulates carbohydrates in leaves and exhibits leaf chlorosis and premature senescence. ACP1 encodes a novel protein that contains two conserved domains of unknown function, DUF4220 and DUF594. Subcellular localization in rice and tobacco showed that ACP1 was localized in the endoplasmic reticulum. In situ expression analysis showed that ACP1 was mainly expressed in vascular bundles. Dye and sugar export experiments suggested that sugar trafficking through vascular tissues was impaired in the acp1 mutant. The acp1 mutant exhibits a significant cellulose deficiency in its leaves. Transmission electron microscopy experiments found that the abnormal cell wall ultrastructure in acp1. Furthermore, turgor pressure in source leaves of acp1 decreased compared with WT. Together, these results suggest that ACP1 plays a critical role in the partitioning of carbohydrates by regulating cell wall formation, which in turn affects the overall carbohydrate distribution and plant physiology.

Elucidating the mechanisms underlying heat tolerance in rice (Oryza Sativa. L) is vital for adapting this crop to rising global temperature while increasing yields. Here, we identified a rice mutant, high temperature tolerance 1 (htt1), with high survival rates under heat stress. HTT1 encodes a chloroplast-localized stearoyl-acyl carrier protein (ACP) desaturase involved in the biosynthesis of unsaturated fatty acids, converting C18:0 to C18:1 fatty acid. Overexpression and knockout rice lines provided evidence that HTT1 negatively regulates the response to heat stress. In the htt1 mutant, a G-to-A base substitution in HTT1 impairs unsaturated fatty acid biosynthesis, remodelling the lipid content of cellular membranes and in particular increasing diglyceride contents, which improves membrane stability under heat stress. HTT1 was differentially expressed in all tissues analyzed and was inhibited by heat. Yeast one-hybrid and dual-luciferase reporter assays showed that OsHsfA2d binds to the promoter of HTT1, inhibiting its expression. Different HTT1 alleles were identified between the two Asian cultivated rice subspecies, indica and japonica, potentially facilitating their adaptation to different environmental temperature. Taken together, these findings demonstrate that HTT1 is a previously unidentified negative regulator of heat tolerance and a potential target gene for the improvement of heat adaptability in rice.

Brassinosteroids (BRs) are polyhydroxylated steroid phytohormones that regulate important agronomic traits, including tiller number in rice (Oryza sativa L.), although the underlying molecular mechanisms remain unclear. Here, we isolated the rice mutant fewer tillers and dwarf 1 (ftd1). Map-based cloning revealed that FTD1 encodes a plant-specific GRAS family protein harboring a conserved GRAS domain at its C-terminus. Genetic and biochemical analyses showed that FTD1 physically interacts with MONOCULM 1 (MOC1) and inhibits its degradation. Genetic analysis also indicated that FTD1 functions as a positive regulator in the BR signaling pathway. Furthermore, OsGSK2 interacts with and phosphorylates FTD1 for degradation via the 26S proteasome. We determined that BRs promote FTD1 accumulation by suppressing OsGSK2 phosphorylation, thus enhancing MOC1 stability for increased tiller number. Our findings reveal an OsGSK2-FTD1-MOC1 regulatory cascade that mediates BR signaling in regulating rice tiller development.

LHC assembly is a fundamental process in forming a peripheral antenna system, which has a significant impact on photosynthesis. However, the molecular mechanism of the LHC assembly still needs to be further investigated in monocotyledonous plants. Here, we identified a bifunctional protein YGL9 in rice, a homolog of cpSRP43 in Arabidopsis, mediates LHC assembly by simultaneously regulating LHCPs transport and chlorophyll synthesis. Mutation of YGL9 exhibits a yellow-green leaf phenotype, with reduced LHCPs contents, impaired photosystem activity and reduced chlorophyll content. YGL9 interacts with cpSRP54 forming the cpSRP complex that transport LHCPs, and YGL9 also interacts with and stabilizes OsGUN4, which is an activator of MgCh and participates in the regulation of chlorophyll synthesis, to synergistically participate in chlorophyll synthesis. Further, genetic evidence demonstrates that YGL9 functions in the same pathway as cpSRP54 and OsGUN4 to regulate LHCPs transport and chlorophyll synthesis. Thus, our study reveals a cross-relationship between LHCPs transport and chlorophyll synthesis, and provides new insights into the LHC assembly process in monocotyledonous plants.

Rice panicle abortion can significantly impact rice yield and food security. Recent research has revealed that panicle abortion is influenced by environmental factors as well as regulated by specific genes. Here we report a novel panicle apical abortion 4 (paa4) mutant with semi-dwarf and panicle apical abortion phenotype, and its abortion occurs when the panicle length is approximately 7 cm. Map-based cloning has identified that PAA4 encodes a Mitogen-activated Protein Kinase Kinase Kinase ε (OsMAPKKKε) protein, and a substitution of G to A in exon 19 of OsMAPKKKε that leads to panicle apical abortion. PAA4 has a higher expression in the spikelet although which expressed in all organs of rice. During panicle growth, excessive Reactive Oxygen Species (ROS) accumulate in the apical panicle of paa4, eventually inducing programmed cell death (PCD). Transcriptome sequencing indicates that PAA4 plays a role in both the generation and elimination of ROS. Therefore, PAA4 might be involved in the balance of ROS at the apical panicle and then affects spikelet development in Oryza sativa.

Tillering is an important agronomic trait of rice (Oryza sativa) that affects the number of effective panicles, thereby affecting yields. The phytohormone auxin plays a key role in tillering. Here we identified the high tillering and semi-dwarf 1 (htsd1) mutant with auxin-deficiency root characteristics, such as shortened lateral roots, reduced lateral root density, and enlarged root angles. htsd1 showed reduced sensitivity to auxin, but the external application of indole-3-acetic acid (IAA) inhibited its tillering. We identified the mutated gene in htsd1 as AUXIN1 (OsAUX1, LOC_Os01g63770), which encodes an auxin influx transporter. The promoter sequence of OsAUX1 contains many SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) binding sites, and we demonstrated that SPL7 binds to the OsAUX1 promoter. TEOSINTE BRANCHED1 (OsTB1), a key gene that negatively regulates tillering, was significantly downregulated in htsd1. Tillering was enhanced in the OsTB1 knockout mutant, and the external application of IAA inhibited tiller elongation in this mutant. Overexpressing OsTB1 restored the multi-tiller phenotype of htsd1. These results suggest that SPL7 directly binds to the OsAUX1 promoter and regulates tillering in rice by altering OsTB1 expression to modulate auxin signaling.

The dynamic balance between the self-renewal and differentiation of stem cells in plants is precisely regulated by a series of developmental regulated genes that exhibit spatiotemporal-specific expression patterns. Several studies have demonstrated that the WOX family transcription factors play critical roles in maintaining the identity of stem cells in Arabidopsis thaliana. In this study, we obtained amiR-WOX9 transgenic plants, which displayed terminating prematurely of shoot apical meristem (SAM) development, along with alterations in inflorescence meristem and flower development. The phenotype of amiR-WOX9 plants exhibited similarities to that of wus-101 mutant, characterized by a stop-and-go growth pattern. It was also found that the expression of WUS in amiR-WOX9 lines was decreased significantly, while in UBQ10::WOX9-GFP transgenic plants, the WUS expression was increased significantly despite no substantial alteration in meristem size compared to Col. Therefore, these data substantiated the indispensable role of WOX9 in maintaining the proper expression of WUS. Further investigations unveiled the direct binding of WOX9 to the WUS promoter via the TAAT motif, thereby activating its expression. It was also found that WUS recognized identical the same TAAT motif cis-elements in its own promoter, thereby repress self-expression. Next, we successfully identified a physical interaction between WOX9 and WUS, and verified that it was harmful to the expression of WUS. Finally, our experimental findings demonstrate that WOX9 was responsible for the direct activating of WUS, which however was interfered by the ways of WUS binding its own promoter and the interaction of WUS and WOX9, thereby ensuring the appropriate expression pattern of WUS and then the stem cell stability. This study contributes to an enhanced comprehension of the regulatory network of the WOX9-WUS module in maintaining the equilibrium of the SAM.

Grain weight, grain number per panicle, and the number of panicles are the three factors that determine rice (Oryza sativa L.) yield. Of these, grain weight, which not only directly determines rice yield but also influences appearance and quality, is often considered the most important for rice production. Here, we describe OsNF-YC1, a member of the NF-Y transcription factor family that regulates rice grain size. OsNF-YC1 knockout plants (osnf-yc1), obtained using CRISPR-Cas9 technology, showed reduced grain weight due to reduced width and thickness, with no change in grain length, leading to a slenderer grain shape. Downregulation of OsNF-YC1 using RNA interference resulted in similar grain phenotypes as osnf-yc1. OsNF-YC1 affects grain formation by regulating both cell proliferation and cell expansion. OsNF-YC1 localizes in both the nucleus and cytoplasm, has transcriptional activation activity at both the N-terminus and C-terminus, and is highly expressed in young panicles. OsNF-YC1 interacts with OsMADS1 both in vivo and in vitro. Further analysis showed that the histone-like structural CBFD-NFYB-HMF domain of OsNF-YC1 conserved in the OsNF-YC transcription factor family can directly interact with the MADS-box domain of OsMADS1 to enhance its transcriptional activation activity. This interaction positively regulates the expression of OsMADS55, the direct downstream target of OsMADS1. Therefore, this paper reveals a potential grain size regulation pathway controlled by an OsNF-YC1-OsMADS1-OsMADS55 module in rice.

BACKGROUND:Leaf morphology is an important component of the idea plant architecture that extensively influences photosynthesis, transpiration, and ultimately grain yield in crops. However, the genetic and molecular mechanisms regulating this morphology remain largely unclear.RESULTS:In this study, a mutant showing a narrow and stripe leaf phonotype, designated nsl2, was obtained. Histological analysis revealed defects in the vascular system and reduced epidermal cell number in the nsl2, while the cell size remained unchanged. Map-based cloning and genetic complementation experiments revealed that NSL2, which encodes a small subunit of ribonucleotide reductases (RNRs), is a null allelic with ST1 and SDL. The NSL2 was expressed in variety of tissues, with the highest levels detected in leaves, and its protein was localized in the nucleus and cytoplasm. The dNTPs level was altered in the nsl2 mutant, and thereby affecting the dNTPs pool balance. In addition, flow cytometric analysis and the altered transcript level of genes related to cell cycle indicated that NSL2 affects cell cycle progression.CONCLUSIONS:Our findings here suggest that NSL2 function in the synthesis of dNTP, the deficient of which leads to DNA synthesis block and in turn affects cell cycle progression, and ultimately decreased cell number and narrow leaf in the nsl2 plant.

The trichomes of rice leaves are formed by the differentiation and development of epidermal cells. Plant trichomes play an important role in stress resistance and protection against direct ultraviolet irradiation. However, the development of rice trichomes remains poorly understood. In this study, we conducted ethylmethane sulfonate (EMS)-mediated mutagenesis on the wild-type (WT) indica rice ‘Xida 1B’. Phenotypic analysis led to the screening of a mutant that is defective in trichome development, designated lhl1 (less hairy leaf 1). We performed map-based cloning and localized the mutated gene to the 70-kb interval between the molecular markers V-9 and V-10 on chromosome 2. The locus LOC_Os02g25230 was identified as the candidate gene by sequencing. We constructed RNA interference (LHL1-RNAi) and overexpression lines (LHL1-OE) to verity the candidate gene. The leaves of the LHL1-RNAi lines showed the same trichome developmental defects as the lhl1 mutant, whereas the trichome morphology on the leaf surface of the LHL1-OE lines was similar to that of the WT, although the number of trichomes was significantly higher. Quantitative real-time PCR (RT-qPCR) analysis revealed that the expression levels of auxin-related genes and positive regulators of trichome development in the lhl1 mutant were down-regulated compared with the WT. Hormone response analysis revealed that LHL1 expression was affected by auxin. The results indicate that the influence of LHL1 on trichome development in rice leaves may be associated with an auxin pathway.

水稻种子快速萌发,可减短吸水膨胀至出土成苗时间,减少有害生物危害,进而有效提高种子成苗率,有利于培养强壮秧苗。为此,本研究对缙恢10号EMS （甲基磺酸乙酯）诱变体库进行了筛选,从中鉴定到一个种子萌发快且矮化多蘖的突变体rgs1,进一步分析发现矮化是由于各节间均缩短造成的,而多蘖则是分蘖芽发育较快引起的。遗传分析表明rgs1的突变性状受单隐性核基因调控,定位区间内叶绿体ζ-胡萝卜素异构酶编码基因LOC＿Os12g21710的第3个外显子发生了G至A的碱基替换,导致蛋白翻译提前终止,从而确定为目的基因。qPCR分析发现,与野生型相比,突变体中独角金内酯（SL）合成基因HTD1、D27、D10及信号传导相关基因D14、TB1的表达均极显著降低,SL信号途径抑制因子D53的表达则极显著升高,表明rgs1矮化多蘖性状与SL缺陷有关。在rgs1中,脱落酸（ABA）合成代谢关键酶基因OsNCED1几乎无表达,MOC3和FON1的表达极显著升高,表明rgs1种子的快速萌发与ABA合成缺陷有关。RGS1可能是水稻体内精准调控SL和ABA协同作用的一个关键基因,从而调控水稻种子萌发、株高、分蘖等的发育。

水稻籽粒大小是一个复杂的农艺性状,受多基因控制。染色体片段代换系是创造自然变异的有效手段,也是复杂性状研究的理想材料。本研究构建了一个新的水稻长大粒染色体片段代换系Z66, Z66以日本晴的基因组为遗传背景,含有来自R225的12个代换片段,平均代换长度为3.32Mb。然后,以日本晴/Z66创建的次级F 2 群体定位出12个控制水稻籽粒大小的QTL,并培育出具有目标QTL的5个新单片段代换系（S1～S5）和4个新双片段代换系（D1～D4）。其中有9个QTL（qGL3、qGL7、qGL10、qGW6、qGW10、qRLW3、qRLW10、qGWT3、qGWT10）可被单片段代换系所验证,表明这些QTL遗传稳定。此外,还利用单片段代换系鉴定到6个新的QTL（qGL9-2、qGW9-2、qRLW6、qRLW7、qRLW9-2、qGWT7）。在这18个QTL中,qGL9-2、qRLW9-1、qRLW9-2、qGW9-2、qGWT9-2可能是新鉴定的QTL。双基因聚合分析表明,不同QTL间聚合产生不同的上位性效应。如qRLW3（a=0.21）和qRLW9-2（a=0.08）聚合产生了0.10的上位性效应,使D2具有比受体日本晴、S1（qRLW3）和S4（qRLW9-2）更大的谷粒长宽比,且差异显著。qGWT3（a=3.99）和qGWT10（a=3.98）聚合产生了-5.35的上位性效应,其遗传效应（2.62）使D3的千粒重比日本晴显著增加,而比S1（qGWT3）和S5（qGWT10）显著减少。了解QTL间的互作效应可对未来基因型的表型进行预测,从而对实现智能型设计育种至关重要。

Grain filling influences grain size and quality in cereal crops. The molecular mechanisms that regulate grain endosperm development remain elusive. In this study, we characterized a filling-defective and grain width mutant, fgw1, whose mutation increased rice seed width mainly via cell division and expansion in grains. Sucrose contents were higher but starch contents lower in the fgw1 mutant during the grain-filling stage, resulting in inferior endosperm of opaque, white appearance with loosely packed starch granules. Map-based cloning revealed that FGW1 encoded a protein containing DUF630/DUF632 domains, localized in the plasma membrane with preferential expression in the panicle. RNA interference in FGW1 resulted in increased grain width and weight, whereas overexpression of FGW1 led to slightly narrower kernels and better grain filling. In a yeast two-hybrid assay, FGW1 interacted directly with the 14–3–3 protein GF14f, bimolecular fluorescence complementation verified that the site of interaction was the membrane, and the mutated FGW1 protein failed to interact with GF14f. The expression of GF14f was down-regulated in fgw1, and the activities of AGPase, StSase, and SuSase in the endosperm of fgw1 increased similarly to those of a reported GF14f-RNAi. Transcriptome analysis indicated that FGW1 also regulates cellular processes and carbohydrate metabolism. Thus, FGW1 regulated grain formation via the GF14f pathway.