Continuously increasing global temperatures present great challenges to food security. Grain size, one of the critical components determining grain yield in rice (Oryza sativa L.), is a prime target for genetic breeding. Thus, there is an immediate need for genetic improvement in rice to maintain grain yield under heat stress. However, quantitative trait loci (QTLs) endowing heat stress tolerance and grain size in rice are extremely rare. Here, we identified a novel negative regulator with pleiotropic effects, Thermo‐Tolerance and grain Length 1 (TTL1), from the super pan‐genomic and transcriptomic data. Loss‐of‐function mutations in TTL1 enhanced heat tolerance, and caused an increase in grain size by coordinating cell expansion and proliferation. TTL1 was shown to function as a transcriptional regulator and localized to the nucleus and cell membrane. Furthermore, haplotype analysis showed that hap^L and hap^S of TTL1 were obviously correlated with variations of thermotolerance and grain size in a core collection of cultivars. Genome evolution analysis of available rice germplasms suggested that TTL1 was selected during domestication of the indica and japonica rice subspecies, but still had much breeding potential for increasing grain length and thermotolerance. These findings provide insights into TTL1 as a novel potential target for the development of high‐yield and thermotolerant rice varieties.

Main conclusion: OsNAC103 negatively regulates rice plant height by influencing the cell cycle and crosstalk of phytohormones. Plant height is an important characteristic of rice farming and is directly related to agricultural yield. Although there has been great progress in research on plant growth regulation, numerous genes remain to be elucidated. NAC transcription factors are widespread in plants and have a vital function in plant growth. Here, we observed that the overexpression of OsNAC103 resulted in a dwarf phenotype, whereas RNA interference (RNAi) plants and osnac103 mutants showed no significant difference. Further investigation revealed that the cell length did not change, indicating that the dwarfing of plants was caused by a decrease in cell number due to cell cycle arrest. The content of the bioactive cytokinin N⁶-Δ²-isopentenyladenine (iP) decreased as a result of the cytokinin synthesis gene being downregulated and the enhanced degradation of cytokinin oxidase. OsNAC103 overexpression also inhibited cell cycle progression and regulated the activity of the cell cyclin OsCYCP2;1 to arrest the cell cycle. We propose that OsNAC103 may further influence rice development and gibberellin–cytokinin crosstalk by regulating the Oryza sativa homeobox 71 (OSH71). Collectively, these results offer novel perspectives on the role of OsNAC103 in controlling plant architecture.

As a major environmental factor, salt stress substantially retards growth and reduces the productivity of rice (Oryza sativa). Members of the DUF1644 family, “the domains of unknown function 1644 motif” are predicted to play an essential regulatory role in response to abiotic stress. However, the specific molecular mechanisms of most members of this family remain elusive. Here, we report that the OsSIDP301 (stress-induced DUF1644 protein) was induced by salt stress and abscisic acid (ABA). We found that overexpression of OsSIDP301 (OE) in plants conferred salt hypersensitivity and reduced grain size, whereas plants with OsSIDP301 RNA interference (RNAi) exhibited salt tolerance and increased grain size in rice. OsSIDP301 determines salt stress tolerance by modulating genes involved in the salt-response and ABA signaling pathways. Further studies suggest that OsSIDP301 regulates grain size by influencing cell expansion in spikelet hulls. Moreover, OsSIDP301 interacts with OsBUL1 COMPLEX1 (OsBC1), which positively regulates grain size in rice. Our findings reveal that OsSIDP301 functions as a negative regulator of salt stress and grain size, and repressing its expression represents a promising strategy for improving salt stress tolerance and yield in rice.

WUSCHEL (WUS) and WUSCHEL-RELATED HOMEOBOX (WOX) proteins determine stem cell maintenance for continual plant growth and development under changing environmental conditions. Nutrient availability is an environmental factor that substantially controls plant growth and development. However, how plant stem cell homeostasis is regulated under nutrient deficiency remains to be elucidated. Here, we showed that cytosolic isocitrate dehydrogenase (ICDH) plays an important role in nutrient sensing of stem cells in Arabidopsis (Arabidopsis thaliana). Nutrient deficiency induced the cytoplasmic-to-nuclear translocation of cytosolic ICDH protein. ICDH can interact with WUS/WOX protein as a complex that further promotes WUS/WOX expression by binding to its promoter. WUS/WOX expression in the icdh-2 mutant was lower than that of wild-type plants under nutrient deficiency. Consistently, loss of ICDH function caused a more serious growth repression under nutrient deficiency that was independent of ICDH’s catalytic activity. Therefore, cytosolic ICDH regulates stem cell homeostasis of plants in response to nutrient deficiency.

Rice, a staple food for over half the global population1, is highly vulnerable to drought stress due to its substantial water requirements, especially amid global climate change. Plants have develo...