Water-Deficit Inducible Expression of a Cytokinin Biosynthetic Gene IPT Improves Drought Tolerance in Cotton

Abstract

Water-deficit stress is a major environmental factor that limits agricultural productivity worldwide. Recent episodes of extreme drought have severely affected cotton production in the Southwestern USA. There is a pressing need to develop cotton varieties with improved tolerance to water-deficit stress for sustainable production in water-limited regions. One approach to engineer drought tolerance is by delaying drought-induced senescence via up-regulation of cytokinin biosynthesis. The isopentenyltransferase gene (IPT) that encodes a rate limiting enzyme in cytokinin biosynthesis, under the control of a water-deficit responsive and maturation specific promoter PSARK was introduced into cotton and the performance of the PSARK::IPT transgenic cotton plants was analyzed in the greenhouse and growth chamber conditions. The data indicate that PSARK::IPT-transgenic cotton plants displayed delayed senescence under water deficit conditions in the greenhouse. These plants produced more root and shoot biomass, dropped fewer flowers, maintained higher chlorophyll content, and higher photosynthetic rates under reduced irrigation conditions in comparison to wild-type and segregated non-transgenic lines. Furthermore, PSARK::IPT-transgenic cotton plants grown in growth chamber condition also displayed greater drought tolerance. These results indicate that water-deficit induced expression of an isopentenyltransferase gene in cotton could significantly improve drought tolerance.

Stress-Induced Cytokinin Synthesis Increases Drought Tolerance through the Coordinated Regulation of Carbon and Nitrogen Assimilation in Rice

“…Under drought stress, plant CK content decreases, and the reduction in CK increases the plant responses to increasing ABA (Davies and Zhang, 1991), inducing stomata closure and inhibiting photosynthesis (Rivero et al, 2010). Our previous results suggested that the stress-induced CK synthesis, driven by a stress-induced promoter, protected against the deleterious effects of water deficit on the photosynthetic apparatus, allowing higher photosynthetic rates and higher yields after water deficit in tobacco (Rivero et al, 2009) and cotton (Gossypium hirsutum; Kuppu et al, 2013) plants grown in the greenhouse and peanut (Arachis hypogaea) plants grown under field conditions (Qin et al, 2011).…”

Conditional up-regulation of cytokinin status increases growth and survival of sugarcane in water-limited conditions

“…Similar results were also reported in IPT transgenic cotton (Kuppu et al, 2013), peanut (Qin et al, 2011) and tobacco (Rivero et al, 2010) with reduced water supply.…”

“…Delayed senescence, increased biomass, increased chlorophyll content and photosynthetic rates (Kuppu et al, 2013) …”

“…In addition to exogenous manipulation, following the discovery of an isopentenyltransferase gene (IPT) from Agrobacterium tumefaciens and its role in cytokinin biosynthesis (Barry et al, 1984), efforts were made to express this gene to up-regulate the production of CK to improve growth under water stress conditions (Kuppu et al, 2013, Qin et al, 2011, Merewitz et al, 2011d, Rivero et al, 2010. The above findings point to potential applications of CK for improving or stabilising agricultural yields where crop growth is limited by water (Ha et al, 2012).…”

Effects of Water Deficit on Growth of Two Tree Species Seedlings in Changbai Mountains of Northeast China

“…The determination of the function of an observed response is one of the most complex issues in plant stress biology. In trying to understand responses to stresses involving a water deficit component, many genes induced by periods of water deficit have been identified and characterized [3][4][5]. In an unfavorable environment, plants must withstand multiple abiotic and biotic stresses, and a response observed during one type of stress may in fact have a role in the amelioration of another condition [6].…”