Chloroplastic SaNADP-ME4 of C3–C4 Woody Desert Species Salsola laricifolia Confers Drought and Salt Stress Resistance to Arabidopsis

The NADP-malic enzyme (NADP-ME) catalyzes the reversible decarboxylation of L-malate to produce pyruvate, CO2, and NADPH in the presence of a bivalent cation. In addition, this enzyme plays crucial roles in plant developmental and environment responses, especially for the plastidic isoform. However, this isoform is less studied in C3–C4 intermediate species under drought and salt stresses than in C3 and C4 species. In the present study, we characterized SaNADP-ME4 from the intermediate woody desert species Salsola laricifolia. SaNADP-ME4 encoded a protein of 646 amino acids, which was found to be located in the chloroplasts based on confocal imaging. Quantitative real-time PCR analysis showed that SaNADP-ME4 was highly expressed in leaves, followed by stems and roots, and SaNADP-ME4 expression was improved and reached its maximum under the 200 mm mannitol and 100 mm NaCl treatments, respectively. Arabidopsis overexpressing SaNADP-ME4 showed increased root length and fresh weight under mannitol and salt stress conditions at the seedling stage. In the adult stage, SaNADP-ME4 could alleviate the decreased in chlorophyll contents and PSII photochemical efficiency, as well as improve the expression of superoxide dismutase, peroxidase, and pyrroline-5-carboxylate synthase genes to enhance reactive oxygen species scavenging capability and proline levels. Our results suggest that SaNADP-ME4 overexpression in Arabidopsis increases drought and salt stress resistance.

Overexpression of the HDA15 Gene Confers Resistance to Salt Stress by the Induction of NCED3, an ABA Biosynthesis Enzyme

Salt stress constitutes a major form of abiotic stress in plants. Histone modification plays an important role in stress tolerance, with particular reference to salt stress resistance. In the current study, we found that HDA15 overexpression confers salt stress resistance to young seedling stages of transgenic plants. Furthermore, salt stress induces HDA15 overexpression. Transcription levels of stress-responsive genes were increased in transgenic plants overexpressing HDA15 (HDA15 OE). NCED3, an abscisic acid (ABA) biosynthetic gene, which is highly upregulated in HDA15 transgenic plants, enhanced the accumulation of ABA, which promotes adaptation to salt stress. ABA homeostasis in HDA15 OE plants is maintained by the induction of CYP707As, which optimize endogenous ABA levels. Lastly, we found that the double-mutant HDA15 OE/hy5 ko plants are sensitive to salt stress, indicating that interaction between HDA15 and ELONGATED HYPOCOTYL 5 (HY5) is crucial to salt stress tolerance shown by HDA15 OE plants. Thus, our findings indicate that HDA15 is crucial to salt stress tolerance in Arabidopsis.

Cloning, Subcellular Location and Expression Analysis of Grape MYB Gene

MYB gene plays an important role in plant growth, development and response to abiotic stress. In this study, the Eurasian grape (Vitis vinifera L.) cultivar ‘Yatomi Rosa’ was used as the test material. Two MYB genes, VvMYBB1 gene and VvMYBA3 gene, were obtained by homologous cloning, and their subcellular location, different organs, and expression patterns under stress treatment and hormone induction were obtained. It was found that VvMYBB1 gene and VvMYBA3 gene proteins were located in the nucleus and belonged to nuclear proteins. VvMYBB1 gene and VvMYBA3 gene were highly expressed in roots and flowers. VvMYBB1 gene and VvMYBA3 gene might have a negative effect on the formation of peel color. VvMYB1 gene and VvMYBA3 gene might play an important role in drought resistance and salt stress resistance in grapes. Under the induction of exogenous hormones, the expression of VvMYBB1 gene was higher than that of VvMYBA3 gene under the treatment of IAA, ETH, SA and MeJA. Expression of VvMYBB1 gene was lower than that of VvMYBA3 gene under the treatment of 6-BA, GA3 and ABA. It showed that MYB gene played an important role in the development of different organs of grapes, fruit coloring and response to abiotic stress. This would provide reference for the utilization of grape MYB gene resources.

Selenium-induced improvements in the ornamental value and salt stress resistance of Plectranthus scutellarioides (L.) R. Br.

Ornamental plants growing in urban areas are often exposed to salt stress that negatively affects their decorative value. Enhancement of their salt resistance to retain a high decorative value despite salt stress has therefore high practical importance. In our study, the exposure of Plectranthus scutellarioides (L.) R. Br. to NaCl-induced moderate (40 mM) or severe salt stress (80 mM) resulted in a number of stress responses including reduced growth parameters, decreased concentration of photosynthetic pigments, and an increase in the accumulation of anthocyanins and free proline. These changes were partially compensated for by the application of selenium (5 µM as Na2SeO4) to the growth medium. However, the beneficial effect of selenium on the growth and physiological parameters of P. scutellarioides was manifested only at the moderate level of salt stress. Under the severe salt stress, the application of selenium was not able to alleviate the phytotoxic effect of NaCl.