Abstract
BackgroundSweet sorghum is an annual C4 crop considered to be one of the most promising bio-energy crops due to its high sugar content in stem, yet it is poorly understood how this plant increases its sugar content in response to salt stress. In response to high NaCl, many of its major processes, such as photosynthesis, protein synthesis, energy and lipid metabolism, are inhibited. Interestingly, sugar content in sweet sorghum stems remains constant or even increases in several salt-tolerant species.ResultsIn this study, the transcript profiles of two sweet sorghum inbred lines (salt-tolerant M-81E and salt-sensitive Roma) were analyzed in the presence of 0 mM or 150 mM NaCl in order to elucidate the molecular mechanisms that lead to higher sugar content during salt stress. We identified 864 and 930 differentially expressed genes between control plants and those subjected to salt stress in both M-81E and Roma strains. We determined that the majority of these genes are involved in photosynthesis, carbon fixation, and starch and sucrose metabolism. Genes important for maintaining photosystem structure and for regulating electron transport were less affected by salt stress in the M-81E line compared to the salt-sensitive Roma line. In addition, expression of genes encoding NADP+-malate enzyme and sucrose synthetase was up-regulated and expression of genes encoding invertase was down-regulated under salt stress in M-81E. In contrast, the expression of these genes showed the opposite trend in Roma under salt stress.ConclusionsThe results we obtained revealed that the salt-tolerant genotype M-81E leads to increased sugar content under salt stress by protecting important structures of photosystems, by enhancing the accumulation of photosynthetic products, by increasing the production of sucrose synthetase and by inhibiting sucrose decomposition.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1760-5) contains supplementary material, which is available to authorized users.
Highlights
Sweet sorghum is an annual C4 crop considered to be one of the most promising bio-energy crops due to its high sugar content in stem, yet it is poorly understood how this plant increases its sugar content in response to salt stress
Effects of salt stress on growth parameters After treated with 50 mM NaCl for 7 days, there was no significant difference in M-81E (Fig. 1a), while growth of Roma was significantly inhibited (Fig. 1b)
In the presence of 150 mM NaCl, the growth of both genotypes was inhibited, but it was more severe in Roma
Summary
Sweet sorghum is an annual C4 crop considered to be one of the most promising bio-energy crops due to its high sugar content in stem, yet it is poorly understood how this plant increases its sugar content in response to salt stress. In response to high NaCl, many of its major processes, such as photosynthesis, protein synthesis, energy and lipid metabolism, are inhibited. Lots of the major processes within plants, such as photosynthesis, protein synthesis, energy metabolism and lipid metabolism are affected [3]. Sweet sorghum has a fast growth rate and high efficiency of biomass accumulation. It is consumed as a food source for humans and as livestock feed. Salt-tolerant genotypes have a greater ability to exclude toxic ions and
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