Stable Expression of mtlD Gene Imparts Multiple Stress Tolerance in Finger Millet

Abstract

Finger millet is susceptible to abiotic stresses, especially drought and salinity stress, in the field during seed germination and early stages of seedling development. Therefore developing stress tolerant finger millet plants combating drought, salinity and associated oxidative stress in these two growth stages is important. Cellular protection through osmotic adjustment and efficient free radical scavenging ability during abiotic stress are important components of stress tolerance mechanisms in plants. Mannitol, an osmolyte, is known to scavenge hydroxyl radicals generated during various abiotic stresses and thereby minimize stress damage in several plant species. In this study transgenic finger millet plants expressing the mannitol biosynthetic pathway gene from bacteria, mannitol-1-phosphate dehydrogenase (mtlD), were developed through Agrobacterium tumefaciens-mediated genetic transformation. mtlD gene integration in the putative transgenic plants was confirmed by Southern blot. Further, performance of transgenic finger millet under drought, salinity and oxidative stress was studied at plant level in T1 generation and in T1 and T2 generation seedlings. Results from these experiments showed that transgenic finger millet had better growth under drought and salinity stress compared to wild-type. At plant level, transgenic plants showed better osmotic adjustment and chlorophyll retention under drought stress compared to the wild-type. However, the overall increase in stress tolerance of transgenics for the three stresses, especially for oxidative stress, was only marginal compared to other mtlD gene expressing plant species reported in the literature. Moreover, the Agrobacterium-mediated genetic transformation protocol developed for finger millet in this study can be used to introduce diverse traits of agronomic importance in finger millet.

Gene Discovery and Advances in Finger Millet [Eleusine coracana (L.) Gaertn.] Genomics—An Important Nutri-Cereal of Future

“…Ceasar and Ignacimuthu (2011) proved the amenability of finger millet to Agrobacterium-mediated gene transfer and developed leaf blast resistant transgenic finger millet plants using rice chtinase gene (Ignacimuthu and Ceasar, 2012; Table 4). Transgenic finger millet plants expressing the mannitol biosynthetic pathway gene mannitol-1-phosphate dehydrogenase ( mtlD ) from bacteria were developed through Agrobacterium tumefaciens -mediated genetic transformation (Hema et al, 2014). The transgenic plants showed better growth under drought and salinity stress compared to wild-type.…”

Transgenic peanut overexpressing mtlD gene confers enhanced salinity stress tolerance via mannitol accumulation and differential antioxidative responses

“…As a strategy for imparting salinity tolerance, overexpressing of mtlD gene coding for MTD has been widely used in various crops (Hema et al 2014;Nguyen et al 2013), including peanut in hydroponic system in our lab (Bhauso et al 2014a). In the present investigation, WT plants exhibited almost negligible, while T lines showed notable MTD activities under salinity stress and non-stress conditions, which suggests the expression of transgene in T lines (Fig.…”

“…Mannitol is a six-carbon, non-cyclic sugar alcohol having different roles like coenzyme regulation, free-radicals scavenging, and osmoregulation (Rahnama et al 2011;Hema et al 2014), thereby imparting abiotic stress tolerance. Synthesis of mannitol takes place in mature leaves, which is then translocated via phloem to heterotrophic sink tissues, where it is either stored or oxidized to mannose through mannitol-1-phosphate dehydrogenase (MTD) and used as a carbon and energy source (Conde et al 2011).…”

“…Among various ways for imparting the salinity tolerance, accumulation of mannitol using E. coli mtlD gene coding for MTD (EC 1.1.1.17), a key mannitol biosynthesis enzyme, has been widely used for the development of transgenic in various crops (Hema et al 2014;Nguyen et al 2013) including peanut (Bhauso et al 2014a, b). Previously, we have reported the successful transfer of mtlD gene in peanut (cv.…”

Drought Adaptation in Millets

“…Hence, this particular gene is useful in adapting the plant to diverse abiotic stresses. Other genes known to be involved in drought response or tolerance in millets were EcDehydrin 7 [80], mt1D [81] and Ec-apx1 [82] from finger millet, and SiARDP [83] from wild foxtail millet.…”