PIF4 promotes water use efficiency during fluctuating light and drought resistance in rice

Abstract

AbstractMolecular mechanism of intrinsic water use efficiency (iWUE) during fluctuating light (FL) was rarely understood. In this study, we investigated five parameters of iWUE under FL in 200 Minicore rice accessions. Among them, a novel trait, WUEFL(averaged iWUE during FL) has highest SNP heritability in these parameters. GWAS identifies six candidate genes, andPIF4is highly expressed in high iWUEFLrice subgroup. Nine SNPs were significantly associated with iWUEFL, and v3 SNP located at -1,075 bp ofPIF4promoter shows highest sensitives to light. Deletion of v3 in a rice cultivar, WYG7 (PIF4v3m) leads to ∼20% reduction in iWUEFL, and overexpressing PIF4 causes 25% increase in iWUEFLunder DS. There are 85% reduction in adenosine 3’,5’-diphosphate (PAP) amounts together with 73% increase inSAL1gene abundance in PIF4v3mthan WYG7. PIF4 transcriptionally repress and activateSAL1andNHX1, respectively, through binding to G-box motifs of the two genes, which leads to 16% reduction and 5% increase in iWUEFLin co-overexpression rice lines ofPIF4-SAL1andPIF4-NHX1, respectively, relative toPIF4-OE under DS. We proposed that PIF4 promotes iWUEFLand stomatal adjustment via targeting the G-box motif ofSAL1andNHX1genes during FL, eventually facilitating to drought resistance.