A long transcript mutant of the rubisco activase gene RCA upregulated by the transcription factor Ghd2 enhances drought tolerance in rice. (3rd March 2022) - Fan, Xiaowei
SUMMARY: The transcription factor Ghd2 increases rice yield potential under normal conditions and accelerates leaf senescence under drought stress. However, its mechanism on the regulation of leaf senescence under drought stress remains unclear. In the present study, to unveil the mechanism, one target of Ghd2, the Rubisco activase gene RCA, was identified through the combined analysis of Ghd2 ‐CRISPR transcriptome data and Ghd2 ‐overexpression microarray data. Ghd2 binds to the 'CACA' motif in the RCA promoter by its CCT domain and upregulates RCA expression. RCA has alternative transcripts, RCAS and RCAL, which are predominantly expressed under normal conditions and drought stress, respectively. Similar to Ghd2‐ overexpressing plants, RCAL‐ overexpressing plants were more sensitive to drought stress than the wild‐type. However, the plants overexpressing RCAS showed a weak drought‐sensitive phenotype. Moreover, RCAL knockdown and knockout plants did not show yield loss under normal conditions, but exhibited enhanced drought tolerance and delayed leaf senescence. The chlorophyll content, the free amino acid content and the expression of senescence‐related genes in the RCAL mutant were lower than those in the wild‐type plants under drought stress. In summary, Ghd2 induces leaf senescence by upregulating RCAL expression under drought stress, and the RCAL mutant has important values in breeding drought‐tolerant varieties. Significance Statement: The CCT domain‐containing protein Ghd2 plays a vital role in controlling rice yield potential and responding to drought stress. In this study, the Rubisco activase gene RCA was identified as the direct target of Ghd2, and the Knockout plants of long transcript of RCA did not have a yield loss under normal condition but enhanced drought tolerance implies that this gene may be a good candidate for breeding cultivars with high yield and drought tolerance.