Abstract
Drought is one of the major environmental constraints affecting the crop productivity worldwide. One of the agricultural challenges today is to develop plants with minimized water utilization and reduced water loss in adverse environmental conditions. Epicuticular waxes play a major role in minimizing water loss. Epicuticular wax covers aerial plant parts and also prevents non-stomatal water loss by forming the outermost barrier from the surfaces. Epicuticular wax content (EWC) variation was found to be affiliated with drought tolerance of groundnut cultivars. In the current study, a fatty acid elongase gene, KCS1, which catalyzes a rate limiting step in the epicuticular wax biosynthesis was isolated from drought tolerant cultivar K-9 and overexpressed in drought sensitive groundnut cultivar (K-6) under the control of CaMV35S constitutive promoter. Transgenic groundnut plants overexpressing AhKCS1 exhibited normal growth and displaying greenish dark shiny appearance. Environmental scanning electron microscopy (ESEM) revealed the excess of epicuticular wax crystal depositions on the transgenic plant leaves compared to non-transgenic wild type plants. The findings were further supported by gas chromotography–mass spectroscopic analysis (GC-MS) that revealed enhanced levels of fatty acids, secondary alcohols, primary alcohols, aldehydes, alkanes, and ketones in transgenics compared to wild types. The AhKCS1 overexpressing transgenic groundnut plants exhibited increase in the cuticular wax content, reduction of water loss, lower membrane damage, decreased MDA content, and high proline content compared to that of non-transgenic groundnut plants. Our findings suggest that the AhKCS1 gene plays a major role in combating drought stress by preventing non-stomatal water loss in drought sensitive groundnut cultivar (K-6).
Highlights
The major limiting abiotic stress factors like drought, salinity, and temperature, affect the growth, development of crop plants, and result in severe crop yield losses (Joshi and Karan, 2013; Fang and Xiong, 2015; Wang et al, 2016)
PCR amplification of AhKCS1 gene resulted in an amplicon of ∼1.4 kb (Supplementary Figure 6)
Phylogenetic analysis affirmed that the AhKCS1 gene corresponds to the condensing enzyme family of KCS (Supplementary Figure 4)
Summary
The major limiting abiotic stress factors like drought, salinity, and temperature, affect the growth, development of crop plants, and result in severe crop yield losses (Joshi and Karan, 2013; Fang and Xiong, 2015; Wang et al, 2016). To cope up with these inimical environmental conditions, plants developed adaptive mechanisms through integrated physiological, biochemical and molecular responses. Tolerance to drought is a complicated event associated with many adaptive traits through which plants would efficiently utilizes moisture under water deprived conditions. Leaf morphology, cuticular wax depositions, and cutinization of the leaf surfaces are important physical adaptations that provide protection to plants against drought (Samuels et al, 2008; Lee and Suh, 2015). The epicuticular wax accumulation on the aerial surfaces is an important adaptation in the course of drought stress seen in several crop plants such as sorghum, peanut, and pea (Sanchez et al, 2001; Samdur et al, 2003; Burow et al, 2008)
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