bHLH57 confers chilling tolerance and grain yield improvement in rice

Abstract

Chilling stress has become a major limiting factor that reduces crop productivity worldwide. In this study, we identified a new gene bHLH57, whose product enhances chilling tolerance in rice at diverse developmental stages. bHLH57 was mainly expressed in leaves and anthers, and its protein was targeted to the nucleus. Overexpression of bHLH57 enhanced chilling tolerance by increasing trehalose synthesis, whereas its mutants by CRISPR/Cas9‐mediated mutagenesis were more sensitive to chilling and had reduced trehalose. Meanwhile, bHLH57 may regulate ROS metabolism and CBFs/DREBs‐ dependent pathways in response to chilling stress. In addition, the overexpression of bHLH57 resulted in increased grain yield under normal and chilling conditions, however, the disruption of bHLH57 displayed decreased grain size and seed setting rate, thus reduced grain yield. Phylogenetic and nucleotide diversity analyses suggested that bHLH57 is relatively conserved in monocotyledons, and may be selected during indica populations adaptation. Taken together, we have identified a new bHLH regulator involved rice chilling tolerance and grain yield, and provide a potential target gene for improving chilling tolerance and grain yield of rice.

Functions of Basic Helix–Loop–Helix (bHLH) Proteins in the Regulation of Plant Responses to Cold, Drought, Salt, and Iron Deficiency: A Comprehensive Review

“…128 Of note, Zhang et al identified a new bHLH regulator, named OsbHLH57, involved rice chilling tolerance and increased grain yield under normal and chilling conditions. 121,122 In banana (Musa acuminate), the overexpression of MaICE1 has been shown to confer cold tolerance. 206 In recent years, there has been more comprehensive research on the interactors of MaICE1, both in vitro and in vivo.…”

“…Additionally, OsWRKY76 interacts with OsbHLH148 and coordinately upregulates the expression of OsDREB1B to enhance cold tolerance . Of note, Zhang et al identified a new bHLH regulator, named OsbHLH57, involved rice chilling tolerance and increased grain yield under normal and chilling conditions. , …”

Prospects for rice in 2050

“…Phenotypic, biochemical, physiological, molecular and cellular understanding of chilling tolerance in rice and novel approaches to speed up molecular design breeding for cold tolerance in rice varieties have been previously reviewed (Li, Zhang, Chong, et al, 2022). However, the ultimate solution to expand rice‐planting to northern areas depends largely on the development of cold/chilling‐tolerant cultivars, which needs mining and exploiting of key genes or alleles Zhang et al reported in this issue that bHLH57 can enhance trehalose synthesis, reactive oxygen species metabolism and CBFs/DREBs‐dependent pathways, acting as a positive regulator of rice chilling tolerance, and that bHLH57 can enhance seed setting rate and seed size, thus increasing grain yield (L. Zhang, Xiang, et al, 2023). Therefore, bHLH57 is a potential target for future breeding for high‐yielding, chilling‐tolerant rice varieties.…”

“…However, O. rufipogon (the ancestor of Asian rice) is perennial. Due to “one‐sow‐one‐harvest” nature, annual rice is not sustainable in many aspects, and particularly vulnerable to changing climates; Due to a more extensive root systems and greater assimilate reserves, perennial rice can better cope with abiotic stress and grow better in more marginal landscapes (Zhang, Huang, et al, 2023). Currently three perennial rice cultivars (PR23, PR25, and PR107) produced by crossing of annual Asian rice with its perennial African relative ( O. longistaminata ) have been released in China.…”

“…Currently three perennial rice cultivars (PR23, PR25, and PR107) produced by crossing of annual Asian rice with its perennial African relative ( O. longistaminata ) have been released in China. A single planting of irrigated perennial rice can be productive for eight consecutive harvests over four years with similar yield of replanted annual rice but much less additional labours, chemicals and seeds (Zhang, Huang, et al, 2023). Perennial rice could be a potential game changer, allowing to supply more rice under changing climates, thus, PR23 was selected as one of the top 10 Science's 2022 Breakthrough of the Year (Pennisi et al, 2022).…”