Cellulosimicrobium funkei strain AR6 alleviate Cr(VI) toxicity in Lycopersicon esculentum by regulating the expression of growth responsible, stress tolerant and metal transporter genes

Chromium (VI) [Cr(VI)] is the predominant environmental pollutant, which adversely affects the growth, physiology and molecular behaviour of the plants. Mitigation of Cr(VI) toxicity in plant by plant growth promoting rhizobacteria (PGPR) is an efficient inexpensive approach. Hence, the present study was designed to elucidate the influence of Cellulosimicrobium funkei AR6 strain on the growth, physico-chemical and transcriptional variations in Lycopersicon esculentum seedlings under Cr(VI) stress. In this study, Cr(VI) exposure reduced the root length (up to 55.50%), shoot length (up to 52.49%) and biomass (up to 57.29%) of L. esculentum, while strain AR6 inoculation significantly increased the above parameters. Moreover, Cr(VI) toxicity increased the production of stress markers such as proline and malondialdehyde (MDA) content in L. esculentum. However, inoculation of C. funkei AR6 strain reduced the production of proline and MDA levels. In gene expression studies, AR6 inoculation influenced the expression of cell wall proliferation LeEXP genes and stabilized the antioxidant system of L. esculentum seedlings by altering the expression of various stress marker genes such as P5CS, DHN, HSP and MT. Besides, strain AR6 down-regulated the major metal transporter NRAMP genes and consequently decreased the Cr accumulation in L. esculentum seedlings by 60.76 and 48.06% at 100 and 200 mu g/ml of Cr(VI) treatment, respectively. Hence, these results suggest that C. funkei AR6 could alleviate Cr(VI) induced toxicity through improving the plant growth, stress tolerance and reducing metal accumulation in L. esculentum.

Automated summary

This study investigated the effects of Cellulosimicrobium funkei AR6 strain on Lycopersicon esculentum seedlings under Cr(VI) stress, showing that the strain can promote plant growth, enhance stress tolerance, reduce metal accumulation, and alleviate Cr(VI)-induced toxicity.