Antagonistic action of PHYA and PHYB is involved in FR-dependent leaf senescence in Arabidopsis accessions

Sensing environmental changes is important for survival of plants, as sessile organisms, in habi-tat. Recently, latitudinal clines in leaf senescence have been reported to be influenced by tem-perature and photoperiod. However, the relationship of light quality with latitudinal response of leaf senescence is still unclear. Here, we found that Arabidopsis accessions in far-red (FR) showed a strong negative correlation of leaf senescence with the latitude of their origin. phyto-chrome A (phyA) and B (phyB) mutants showed early and delayed senescence in FR, respec-tively, suggesting that PHYA and PHYB are involved in FR-dependent leaf senescence. Tran-scriptomic analysis identified genes oppositely regulated by PHYA and PHYB, and they were mainly associated with phytohormone, temperature, and defense, suggesting their associations with FR-dependent antagonistic effects of PHYA and PHYB on leaf senescence. Among these genes, the expression of WRKY6 in Arabidopsis accessions showed the highest correlation with latitude of their origin. Consistently, wrky6 mutant exhibited delayed senescence phenotype in FR. In conclusion, we propose that PHYs-regulated genes, including WRKY6, are involved in latitudinal leaf senescence in FR and this regulatory mode may contribute to latitudinal adapta-tion by responding FR, as a piece of geographical information. We measured gene expression in phyA-211 and phyB-9 mutants, and Col-0 before and after Far-red light treatment (730 nm, 1μmol m-2s-1; 0 and 4 days). We used biological duplicates for each condition