GhLIP1, a lipoic acid synthase gene, negatively regulates leaf senescence in cotton

Abstract

Leaves are the key organs of plants that produce photosynthates. Leaf senescence aids nutrient remobilization from source to sink tissues, which dramatically affects crop quality and yield. Although several senescence-associated genes (SAGs) have been recognized in cotton, the function of lipoic acid synthase in leaf senescence remains unclear. Therefore, we isolated a lipoic acid synthase gene named GhLIP1 from cotton (Gossypium hirsutum L.). Protein domain analysis revealed that GhLIP1 had a LIAS-N domain and an Elp3 domain, and yeast mutant complementation experiments demonstrated that GhLIP1 was a lipoic acid synthase. GhLIP1 expression pattern analysis showed that GhLIP1 was vastly expressed in fibres, and the phytohormone IAA (indole-3-acetic acid) induced its transcription. When GhLIP1 was transformed into Arabidopsis, the leaves of overexpression Arabidopsis exhibited a late leaf senescence phenotype compared to wild-type Arabidopsis, Col-0. Moreover, downregulation of GhLIP1 expression using virus-induced gene silencing (VIGS) technology resulted in early leaf senescence in cotton. qRT-PCR analyses revealed that two SAGs, GhWRKY53 and GhNAP, were upregulated in cotton plants with GhLIP1 knock-down. Cell ultrastructure observations found that chloroplasts were degraded in an orderly manner in cotton leaf cells with GhLIP1 knock-down. These results suggest that GhLIP1 plays a significant role in leaf senescence in cotton.