Abstract
BackgroundPlant response mechanisms to heat and drought stresses have been considered in strategies for generating stress tolerant genotypes, but with limited success. Here, we analyzed the transcriptome and improved tolerance to heat stress and drought of maize plants over-expressing the OsMYB55 gene.ResultsOver-expression of OsMYB55 in maize decreased the negative effects of high temperature and drought resulting in improved plant growth and performance under these conditions. This was evidenced by the higher plant biomass and reduced leaf damage exhibited by the transgenic lines compared to wild type when plants were subjected to individual or combined stresses and during or after recovery from stress. A global transcriptomic analysis using RNA sequencing revealed that several genes induced by heat stress in wild type plants are constitutively up-regulated in OsMYB55 transgenic maize. In addition, a significant number of genes up-regulated in OsMYB55 transgenic maize under control or heat treatments have been associated with responses to abiotic stresses including high temperature, dehydration and oxidative stress. The latter is a common and major consequence of imposed heat and drought conditions, suggesting that this altered gene expression may be associated with the improved stress tolerance in these transgenic lines. Functional annotation and enrichment analysis of the transcriptome also pinpoint the relevance of specific biological processes for stress responses.ConclusionsOur results show that expression of OsMYB55 can improve tolerance to heat stress and drought in maize plants. Enhanced expression of stress-associated genes may be involved in OsMYB55-mediated stress tolerance. Possible implications for the improved tolerance to heat stress and drought of OsMYB55 transgenic maize are discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2659-5) contains supplementary material, which is available to authorized users.
Highlights
Plant response mechanisms to heat and drought stresses have been considered in strategies for generating stress tolerant genotypes, but with limited success
Seedlings from WT and two OsMYB55 transgenic lines were used to make an initial assessment of their growth in response to high temperature
Growth reduction of transgenic plants was less affected than WT after five days of heat treatment, reflected by a small reduction of dry biomass, plant height, and stem diameter (Fig. 1)
Summary
Plant response mechanisms to heat and drought stresses have been considered in strategies for generating stress tolerant genotypes, but with limited success. Similar to reacting to drought and salinity, plants deploy various protection mechanisms to endure heat stress (HS) including scavenging of ROS, production of antioxidants, accumulation of compatible solutes and activating signaling cascades leading to the synthesis of molecular chaperones such as heat-shock proteins (HSPs) and late embryogenesis abundant (LEA) proteins. These chaperones would prevent denaturation of existing proteins, misfolding of newly synthesized proteins and maintaining membrane stability [8]. All these response mechanisms have been considered in strategies for improving heat tolerance through modern breeding protocols and biotechnological approaches, though up to now their success has been limited
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