Analysis Reveals the Differential Expression of Genes Related to Starch Accumulation in Chloroplast of Leaf with Different Ages in Pinot Noir Grape

The accumulation of starch in chloroplast of grape leaves increased with leaf maturation, but the related molecular mechanism has not been reported. In this study, the potential related genes were screened in order to clarify the molecular regulation mechanism of starch accumulation in chloroplast of grape leaves with different leaf ages.

Two years old ‘Pinot Noir’ grapes (Vitis vinifera L.) were used as plant materials to investigate the dynamic changes of starch accumulation in chloroplast of leaves with different ages. The RNA sequencing technology was used to characterize the differently expressed genes (DEGs) involved in starch and sucrose metabolism in leaves with different ages. The expression levels of several key candidate genes were detected by using real-time quantitative qPCR.

The starch grains in NL (undeveloped leaves) were smallest in volume and lowest in number compared with these in GL (growing leaves) and ML (mature leaves). With the increase of leaf ages, the volume and amount of starch grains in GL and ML also increased. A total of 58.57 GB valid data was obtained by RNA-sequencing. Differentially expressed genes mainly involved in starch and sucrose metabolism pathway for the leaves with different ages. The genes involved in the process of sucrose conversion into starch synthesis precursor adenosine diphosphate glucose (ADP) showed up-regulated expression level with the increase of leaf ages, including cell wall invertase (CWINV), phosphoglucomutase (PGM), and ADP-glucose pyrophosphorylase (AGPase). The genes involved in starch synthesis and hydrolysis also presented up-regulated expression level with the increase of leaf ages, including soluble starch synthase (SSⅠ), starch branching enzyme (SBE), α-amylase (AMY), and β-amylase (BAM). AGPase, SSⅠ and SBE played an important role in synthesis of amylopectin with semi-crystalline structure.

With the increase of leaf ages, the starch accumulation in chloroplast also increased. AGPase, SSⅠ and SBE genes could be the key genes involved in the regulation of starch accumulation in chloroplast of grape leaves.