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

Background: 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.

Methods And Results: 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.

Conclusion: 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.