Salt and drought stress tolerance with increased biomass in transgenic Pelargonium graveolens through heterologous expression of ACC deaminase gene from Achromobacter xylosoxidans

Geranium (Pelargonium graveolens) is a strongly aromatic medicinal plant with increasing market demand. The present study demonstrated that the transgenic P. graveolens exhibited a remarkable increase in plant height (~20–23%), total biomass (18–60%), leaf: stem ratio (12–21%) and quantity of oil, compared to its wild-type counterpart. Transgenic P. graveolens expressing ACC deaminase gene from Achromobacter xylosoxidans, encoding 1-aminocyclopropane-1-carboxylilate under the control of 35 S CaMV promoter showed immense tolerance to salinity and drought stress than the wild-type plant. Parameters examined were chlorophyll content, photosynthetic parameters, relative water content (RWC), ROS production, antioxidants, proline, ACC content and real time analysis of ACC synthase, ACC deaminase, and ACC oxidase genes. The ACC deaminase-expressing transgenic lines viz. L1, L5 and L7 demonstrate a decrease of ACC content under salt and drought stress, which could lead increased ethylene production, which in turn may affect salt and drought stress. Transgenic P. graveolens showed enhanced tolerance to salt and drought stress as reflected as a result of higher leaf RWC, chlorophyll content, photosynthetic parameter, accumulation of proline and more antioxidant activity. The reported transgenic P. graveolens lines are potentially valuable materials for cultivation in saline and drought-prone areas. In this manuscript we are reporting successful production of transgenic P. graveolens with acc deaminase gene of bacterial origin. The transgenic plant has shown increase in biomass, high leaf: stem ratio, enhanced tolerance to salt and drought stress with better economic yield.