Effect of over-and under-expression of glyceraldehyde 3-phosphate dehydrogenase on tolerance of plants to water-deficit stress

Abstract

While involved in a functional genomics program, we found that the overexpression of potato (Solanum tuberosum) glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene in yeast improves its water-deficit stress (drought) tolerance. But, the effect of altered (under and over) expression of GAPDH on water-deficit stress tolerance of higher plants is not yet studied. In this study, we used a versatile reverse genetics tool called virus-induced gene silencing and down-regulated the expression of GAPDH gene in tobacco (Nicotiana benthamiana) to examine the relevance (effect of underexpression) of GAPDH on drought tolerance of higher plants. Leaf discs made from silenced and nonsilenced tobacco plants were subjected to water-deficit stress. Measure of cell viability and the content of chlorophyll in stressed and nonstressed leaf discs were determined to quantify the effect of stress. Leaf discs made from the gene-silenced plants were found to be more severely affected by the stress than the leaf discs made from nonsilenced plants, implying the importance of GAPDH gene in drought tolerance of plants. Furthermore, to reiterate the involvement of GAPDH in drought tolerance of plants, potato transgenic plants constitutively overexpressing the GAPDH gene were generated and their performance under drought condition was analyzed. Transgenic potato plants showed improved drought tolerance when compared to wild-type potato. On the whole, our results confirm that the GAPDH gene plays an important role in drought tolerance of higher plants, and its constitutive overexpression by genetic engineering can be used to improve drought tolerance of crop plants like potato.