Improved drought tolerance in wheat plants overexpressing a synthetic bacterial cold shock protein gene SeCspA.

Cold shock proteins (CSPs) enhance acclimatization of bacteria to adverse environmental circumstances. The Escherichia coli CSP genes CspA and CspB were modified to plant-preferred codon sequences and named as SeCspA and SeCspB. Overexpression of exogenous SeCspA and SeCspB in transgenic Arabidopsis lines increased germination rates, survival rates, and increased primary root length compared to control plants under drought and salt stress. Investigation of several stress-related parameters in SeCspA and SeCspB transgenic wheat lines indicated that these lines possessed stress tolerance characteristics, including lower malondialdehyde (MDA) content, lower water loss rates, lower relative Na+ content, and higher chlorophyll content and proline content than the control wheat plants under drought and salt stresses. RNA-seq and qRT-PCR expression analysis showed that overexpression of SeCsp could enhance the expression of stress-responsive genes. The field experiments showed that the SeCspA transgenic wheat lines had great increases in the 1000-grain weight and grain yield compared to the control genotype under drought stress conditions. Significant differences in the stress indices revealed that the SeCspA transgenic wheat lines possessed significant and stable improvements in drought tolerance over the control plants. No such improvement was observed for the SeCspB transgenic lines under field conditions. Our results indicated that SeCspA conferred drought tolerance and improved physiological traits in wheat plants.

A R2R3-MYB transcription factor gene in common wheat (namely TaMYBsm1) involved in enhancement of drought tolerance in transgenic Arabidopsis.

We isolated the TaMYBsm1 genes, encoding R2R3-type MYB proteins in common wheat, aimed to uncover the possible molecular mechanisms related to drought response. The TaMYBsm1 genes, TaMYBsm1-A, TaMYBsm1-B and TaMYBsm1-D, were isolated and analyzed from the common wheat cultivar Shimai 15. Their expression patterns under PEG 6000 and mannitol were monitored by semi-quantitative RT-PCR and ß-glucuronidase (Gus) assay. The function of TaMYBsm1-D under drought stress in transgenic Arabidopsis plants was investigated, and the germination rate, water loss rate, as well as the proline and malondialdehyde (MDA) content were compared with that in wild type (WT) plants. The expression of three downstream genes (DREB2A, P5CS1 and RD29A) in TaMYBsm1-D transgenic plants was analyzed. The R2R3-MYB domains of the MYBsm1 proteins were highly conserved in plants. In addition, the TaMYBsm1 proteins were targeted to the nucleus and contained transcriptional activation domains (TADs). Gus assay and semi-quantitative RT-PCR analysis demonstrated that the TaMYBsm1 genes were up-regulated when the wheat was treated by PEG and mannitol. Compared with WT plants, the germination rates were much higher, but the water loss rates were much lower in TaMYBsm1-D overexpression plants. TaMYBsm1-D transgenic plants showed distinct higher proline contents but a lower MDA content than the WT plants. The three downstream genes were highly expressed in TaMYBsm1-D transgenic plants. We concluded from these results that TaMYBsm1 genes play an important role in plant drought stress tolerance through up-regulation of DREB2A, P5CS1 and RD29A. The increase of proline content and decrease of MDA content may also be involved in the drought response.