Differential gene expression analysis reveals the fast-growth mechanisms in Melia dubia at different stand ages

Melia dubia Cav. is a fast-growing multipurpose tree suitable for agroforestry and has been widely cultivated for wood-based industries, particularly pulp and paper production. Despite its high economic value in India, there is a lack of information regarding the molecular mechanism driving its fast-growth. Therefore, this study aimed to elucidate the molecular mechanisms responsible for fast-growth by expression analysis of selective candidate genes. Initially, growth traits were assessed, including tree height and diameter at breast height (DBH), across three different ages (one-year-old, two-year-old, and three-year-old) of M. dubia plantations. Tree volume based on tree height and DBH, was also calculated. The analysis of annual tree height increment revealed that the second-year plantation exhibited the higher increment, followed by first and third years. In contrast, DBH was maximum in third-year plantation, followed by the second and first years. Similarly, annual tree volume increment showed a similar trend with DBH that maximum in the third year, followed by second and first years. Furthermore, a differential gene expression analysis was performed using qRT-PCR on four genes such as Phloem Intercalated with Xylem (PXY), Clavata3/Embryo Surrounding Region-Related 41 (CLE41), 1-aminocyclopropane-1-carboxylic acid synthase (ACS-1) and Hemoglobin1 (Hb1) for downstream analysis. The relative gene expression showed up-regulation of CLE41, ACS-1, and Hb1 genes, while the PXY gene was downregulated across the tree ages. Interestingly, a positive association was observed between tree growth and the expression of the selected candidate genes. Our results pave the way for further research on the regulatory mechanisms of genes involved in fast-growth and provide a basis for genetic improvement of Melia dubia.