A Truncated ETHYLENE INSENSITIVE3/EIN3-Like protein, GhLYI, Regulates Senescence in Cotton.

Numerous endogenous and environmental signals regulate the intricate and highly orchestrated process of plant senescence. Ethylene (ET), which accumulates as senescence progresses, is a major promoter of leaf senescence.The master transcription activator ETHYLENE INSENSITIVE3 (EIN3) activates the expression of a wide range of downstream genes during leaf senescence. Here, we found that a unique EIN3-LIKE 1 (EIL1) gene, Cotton LINT YIELD INCREASING (GhLYI), encodes a truncated EIN3 protein in upland cotton (Gossypium hirsutum L.) that functions as an ET signal response factor and a positive regulator of senescence. Ectopic expression or overexpression of GhLYI accelerated leaf senescence in both Arabidopsis (Arabidopsis thaliana) and cotton. Cleavage under targets and tagmentation (CUT&Tag) analyses revealed SENESCENCE-ASSOCIATED GENE 20 (SAG20) was a target of GhLYI. Electrophoretic mobility shift assay (EMSA), yeast one-hybrid (Y1H), and dual-luciferase transient expression assay confirmed that GhLYI directly bound the promoter of SAG20 to activate its expression. Transcriptome analysis revealed that transcript levels of a series of senescence related genes, SAG12, NAC LIKE, ACTIVATED by APETALA 3/PISTILLATA (NAP/ANAC029), and WRKY53, are substantially induced in GhLYI overexpression plants compared with wild-type plants. VIGS(Virus-induced gene silencing) preliminarily confirmed that knockdown of GhSAG20 delayed leaf senescence. Collectively, our findings provide a regulatory module involving GhLYI-GhSAG20 in controlling senescence in cotton.