ABSTRACT
We investigated whether the presence of anthocyanins in plants could contribute to low pH stress tolerance using anthocyanin-enriched transgenic petunia lines (PM2, PM6, and PM8) expressing RsMYB1 and wild-type (WT) plants. We examined several physiological and biochemical factors and the transcript levels of genes involved in abiotic stress tolerance. A reduction in plant growth, including plant height and fresh weight, was observed when plants (PM2, PM6, PM8, and WT) were exposed to low pH (pH 3.0) conditions compared to growth under normal (pH 5.8) conditions. A small reduction in the growth of PM6 was observed, followed by that in PM2, PM8, and WT, reflecting the anthocyanin levels in the plants (PM6 > PM2 and PM8 > WT). An analysis of physiological and biochemical factors also supports the degree of low pH tolerance in the plants (PM6 > PM2 and PM8 > WT). In addition, an enhanced expression of the genes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), osmotin, and vacuolar H+-ATPase (V-ATPase)] was observed in the transgenic lines (PM2, PM6, and PM8). The resultant of the enhanced transcript levels of the genes could promote antioxidant activities, proline content, and pH homeostasis involved in the mechanisms underlying abiotic stress tolerance in plants. These results suggest that anthocyanin-enriched plants overexpressing RsMYB1 enhances low pH stress tolerance by elevating the transcript levels of the relevant genes.
ABSTRACT
The co-expression of Rosea1 (Ros1) and Delila (Del) regulates anthocyanin levels in snapdragon flowers, as well as in tomato, petunia, and tobacco. However, there is little information on how Ros1 expression alone controls anthocyanin regulation and whether it is involved in the mechanism that leads to abiotic stress tolerance. In the present study, tobacco (Nicotiana tabacum 'Xanthi') transgenic plants overexpressing Ros1 (T2-Ros1-1, T2-Ros1-2, T2-Ros1-3, and T2-Ros1-4) promoted accumulation of anthocyanin in leaves and flowers by elevating the transcription of all key genes involved in the biosynthesis of this pigment. This promotion largely occurred through the upregulation of dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase genes in leaves and upregulation of DFR in flowers. Under normal conditions, the transgenic lines and wild type (WT) plants showed well-developed broad leaves and regular roots, whereas a reduction in plant growth was observed under cold and drought stresses. However, the transgenic T2-Ros1 lines were able to tolerate the stresses better than the WT line by inducing reactive oxygen species scavenging activities, and the expression of antioxidant-related and stress-responsive genes. In addition, phylogenetic analysis clustered Ros1 with many transcription factors (TFs) that confer tolerance to different abiotic stresses. Overall, the results obtained here suggest that Ros1 overexpression upregulates anthocyanin biosynthetic, antioxidant-related, and stress-responsive genes thereby enhancing anthocyanin accumulation and abiotic stress tolerance.
ABSTRACT
We investigated the role of nano-silver (NAg) and the bacterial strain Enterobacter cloacae in increasing the vase life of cut carnation flowers 'Omea.' NAg treatment extended vase life of the flowers by increasing relative fresh weight, antioxidant activities, and expression level of the cysteine proteinase inhibitor gene (DcCPi), and by suppressing bacterial blockage in stem segments, ethylene production and expression of ethylene biosynthesis genes and DcCP1 gene, compared with the control. Out of all the treatments, administration of 25 mg L-1 NAg gave the best results for all the analyzed parameters. Interestingly, application of E. cloacae also extended the vase life of cut flowers by 3 days in comparison with control flowers, and overall, showed better results than the control for all the analyzed parameters. Taken together, these results demonstrate the positive role of NAg and E. cloacae in increasing the longevity of cut carnation flowers, and indicate that this effect is brought about through multiple modes of action.
