In plants, auxin/indoleacetic acid (Aux/IAA) proteins are transcriptional regulators that regulate developmental process and responses to phytohormones and stress treatments. However, the regulatory functions of the Vitis vinifera L. (grapevine) Aux/IAA transcription factor gene VvIAA18 have not been reported. In this study, the VvIAA18 gene was successfully cloned from grapevine. Subcellular localization analysis in onion epidermal cells indicated that VvIAA18 was localized to the nucleus. Expression analysis in yeast showed that the full length of VvIAA18 exhibited transcriptional activation. Salt tolerance in transgenic tobacco plants and Escherichia. coli was significantly enhanced by VvIAA18 overexpression. Real-time quantitative PCR analysis showed that overexpression of VvIAA18 up-regulated the salt stress-responsive genes, including pyrroline-5-carboxylate synthase (NtP5CS), late embryogenesis abundant protein (NtLEA5), superoxide dismutase (NtSOD), and peroxidase (NtPOD) genes, under salt stress. Enzymatic analyses found that the transgenic plants had higher SOD and POD activities under salt stress. Meanwhile, component analysis showed that the content of proline in transgenic plants increased significantly, while the content of hydrogen peroxide (H2O2) and malondialdehyde (MDA) decreased significantly. Based on the above results, the VvIAA18 gene is related to improving the salt tolerance of transgenic tobacco plants. The VvIAA18 gene has the potential to be applied to enhance plant tolerance to abiotic stress.

Dihydroflavonol 4-reductase (DFR) is a key enzyme in the flavonoid biosynthetic pathway and is essential for the formation of plants’ color. In this study, 26 BnDFR genes were identified using 6 Arabidopsis DFR genes as reference. The physicochemical properties, subcellular localization, and conserved structure of BnDFR proteins were analyzed; the evolutionary relationship, collinearity analysis, and expression characteristics of BnDFR genes were studied; and the correlation between the expression level of BnDFR genes and anthocyanin content in rape petals were analyzed. The results showed that the 26 BnDFRs were located in chloroplasts, cytoplasm, nuclei, and mitochondria, distributed on 17 chromosomes, and divided into 4 groups; members of the same group have a similar function, which may be related to the environmental response elements and plant hormone response elements. Intraspecific collinearity analysis showed 51 pairs of collinear genes, and interspecific collinearity analysis showed 30 pairs of collinear genes. Analysis of the expression levels of BnDFRs and anthocyanin content in different color rape petals showed that BnDFR6 and BnDFR26 might play an important role in the synthesis of anthocyanins in rape petals. This provides theoretical guidance for further analysis of the anthocyanin anabolism mechanism involved in the DFR gene in Brassica napus.

Rapeseed is an important oil crop in China. Low winter temperatures (LT) often limit plant growth and cause seed yield losses in rapeseed. Although exogenous application of 5-aminolevulinic acid (ALA) has been shown to enhance plant tolerance to various abiotic stressors, its physiological mechanisms for improving cold tolerance in rapeseed are not yet fully understood. In this study we investigated the physiological responses to exogenous ALA using the chilling-tolerant cultivar Zayou15 (ZY15) and the chilling-sensitive cultivar Huiyou 49 (HY49) under low-temperature stress. The results showed that low-[A1] temperature stress caused a considerable decrease the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as in the contents of endogenous hormones GA, IAA, and CTK. These resulted in the accumulation of reactive oxygen species, with both the content of H2O2 and O2- showing considerable increases, as well as in membrane lipid peroxidation with considerable increases in both malondialdehyde content (MDA) and relative electrical conductivity (REC). Moreover, the contents of chlorophyll（Chl）b, Chl a/Chl b, transpiration rate (Tr), net photosynthesis (Pn), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) were considerably decreased by low-temperature stress, resulting in remarkable growth inhibition (with the aboveground fresh weight significantly decreased). Although, 20 mgL-1 exogenous ALA significantly reduced O2-, H2O2, and MDA content, and REC in both cultivars; it did not increase POD, SOD, CAT, or ascorbic acid peroxidase (APX) under short-term low-temperature stress (12–48 h). However, ALA substantially increased the activities of GA, Pn, Tr, Gs and Ci, resulting in a considerable increase in aboveground fresh weight. Post-treatment spraying of rapeseed plants with 5 mL of 20 mg·L-1 ALA was more effective than pre-treatment spraying. Both cultivars sprayed with ALA post-treatment showed greater reduction in MDA content. The optimum ALA dosage and concentration were 5 mL and 20 mg·L-1, respectively, leading to considerable decrease in MDA, and REC content and increase in Chl content in leaves. In conclusion, our results demonstrate that exogenous application of ALA is an appropriate strategy for rapeseed to resist winter low-temperature stress.