Physiological and Transcriptomic Changes During Autumn Coloration and Senescence in Ginkgo biloba Leaves

Autumn leaf senescence and coloration is a complex process and a striking natural phenomenon. Here, through biology approach integrating transcriptomic analyses in Ginkgo biloba, we determined that the content of chlorophyll decreased during leaf senescence, while carotenoid components increased until late October in the turning stage (TS) and then decreased in the yellow leaf stage (YS). Simultaneously, chlorophyll biosynthesis genes exhibited significantly lower expression levels while chlorophyll degradation genes showed increased expression from the green leaf stage (GS) to YS. However, carotenoid biosynthesis-related genes showed enhanced expression, especially in TS. An analysis of the expression of genes related to senescence demonstrated that the expression levels of most abscisic acidand jasmonic acid-related genes, autophagy, WRKY, and NAC genes increased, whereas cytoskeleton-, photosynthesis-, and antioxidation-related genes decreased from GS to YS. Furthermore, G . biloba seedlings exogenously treated with abscisic acid, jasmonic acid, or ultraviolet-B radiation all showed obvious color variation and senescence symptoms. We used these exogenously seedlings to further validate the function of several genes involved in chlorophyll biosynthesis and senescence. Taken together, these results contribute to the elucidation of the molecular mechanisms of leaf coloration and senescence in G . biloba as well as in the identification of candidate genes involved in this process.