Genetic redundancy of senescence-associated transcription factors in Arabidopsis.

Leaf senescence is a genetically programmed process that constitutes the last stage of leaf development, and involves massive changes in gene expression. As a result of the intensive efforts that have been made to elucidate the molecular genetic mechanisms underlying leaf senescence, 184 genes that alter leaf senescence phenotypes when mutated or overexpressed have been identified in Arabidopsis thaliana over the past two decades. Concurrently, experimental evidence on functional redundancy within senescence-associated genes (SAGs) has increased. In this review, we focus on transcription factors that play regulatory roles in Arabidopsis leaf senescence, and describe the relationships among gene duplication, gene expression level, and senescence phenotypes. Previous findings and our re-analysis demonstrate the widespread existence of duplicate SAG pairs and a correlation between gene expression levels in duplicate genes and senescence-related phenotypic severity of the corresponding mutants. We also highlight effective and powerful tools that are available for functional analyses of redundant SAGs. We propose that the study of duplicate SAG pairs offers a unique opportunity to understand the regulation of leaf senescence and can guide the investigation of the functions of redundant SAGs via reverse genetic approaches.