Heterologous expression of ACC deaminase gene in Pelargonium graveolens showed elevated tolerance to chromium stress.

An essential aromatic plant, Pelargonium graveolens, does not grow well in areas where chromium contamination is a problem. Because of oxidative stress and the collapse of the photosynthetic system, crops frequently sustain severe damage. The production of excess ethylene, known as stress ethylene, which is detrimental to plant growth, the formation of roots, and early senescence, is also increased by heavy metal exposure. The effectiveness of the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase gene in transgenic Pelargonium graveolens under the control of CaMV 35S promoter was investigated to lessen the stress ethylene during chromium stress. Chromium was administered as potassium dichromate (K₂Cr₂O₇) at four distinct concentrations (100 µM, 200 µM, 300 µM, and 500 µM) to transgenic and wild-type P. graveolens and stress-induced physiological changes were monitored. Transgenic P. graveolens demonstrated greater tolerance to chromium stress than wild-type P. graveolens, as evidenced by higher leaf-relative water content, chlorophyll content, CO₂ absorption, transpiration rate, stomatal conductance, proline buildup, and antioxidant activity. The L1, L5, and L7, ACC deaminase-expressing transgenic lines also show a drop in ACC content during chromium stress, which subsequently lowered ethylene synthesis. Therefore, the reported transgenic P. graveolens lines having the ACC deaminase gene could be useful resources for growing in chromium-prone regions.