Yujian Mo, Guangyan Li, Li Liu, Yingjie Zhang, Junyi Li, Meizhen Yang, Shanlan Chen, Qiaoling Lin, Guanfu Fu, Dianfeng Zheng, Yu Ling

Front Plant Sci.; 2023 Feb 22; 14:1121852. doi: 10.3389/fpls.2023.1121852. 

Abstract

Extreme high temperature at the meiosis stage causes a severe decrease in spikelet fertility and grain yield in rice. The rice variety grain size on chromosome 2 (GS2) contains sequence variations of OsGRF4 (Oryza sativa growth-regulating factor 4; OsGRF4^AA ), escaping the microRNA miR396-mediated degradation of this gene at the mRNA level. Accumulation of OsGRF4 enhances nitrogen usage and metabolism, and increases grain size and grain yield. In this study, we found that pollen viability and seed-setting rate under heat stress (HS) decreased more seriously in GS2 than in its comparator, Zhonghua 11 (ZH11). Transcriptomic analysis revealed that, following HS, genes related to carbohydrate metabolic processes were expressed and regulated differentially in the anthers of GS2 and ZH11. Moreover, the expression of genes involved in chloroplast development and photosynthesis, lipid metabolism, and key transcription factors, including eight male sterile genes, were inhibited by HS to a greater extent in GS2 than in ZH11. Interestingly, pre-mRNAs of OsGRF4, and a group of essential genes involved in development and fertilization, were differentially spliced in the anthers of GS2 and ZH11. Taken together, our results suggest that variation in OsGRF4 affects proper transcriptional and splicing regulation of genes under HS, and that this can be mediated by, and also feed back to, carbohydrate and nitrogen metabolism, resulting in a reduction in the heat tolerance of rice anthers.

See https://pubmed.ncbi.nlm.nih.gov/36909437/

Figure 6 Expressions of growth regulation factors (GRFs) under different temperature conditions. (A) Expression patterns of GRFs in RNA sequencing (RNA-Seq) data. (B) Expression of OsGRF4 (Oryza sativa growth-regulating factor 4) measured by reverse transcription-quantitative PCR (qRT-PCR). (C) Visualization of coverage of sequencing reads annotated to OsGRF4 gene using the IGV program. (D) Reverse transcription-PCR (RT-PCR) validation of the intron retention (IR) event detected in OsGRF4. (E) RT-PCR amplification of OsGRF4 by using leaf cDNA as a template. (F) Amino acid residues of the conventional OsGRF4 protein and that of the potential protein variant translated from the intron-retained mRNA isoform. Only amino acid residues from position 380 on are shown. * stands for the terminal point of the amino acid sequence.