Response and Function of Solanum lycopersicum L. SlSGR2 Gene under Cadmium Stress

Abstract

Cd stress can cause severe damage to the chloroplast structure and plant function. The chloroplast stay-green gene (SGR2) is senescence-inducible and has several important functions such as regulating senescence, responding to abiotic stress, and regulating seed and fruit ripening. The SlSGR2 gene was cloned from the tomato “Hongluocheng” (full-length of 819 bp encoding 272 amino acids). Subcellular localization prediction and laser confocal observation revealed that the SlSGR2 protein was localized to the chloroplast of A. thaliana protoplasts. A qRT-PCR analysis suggested that the SlSGR2 gene was upregulated by different Cd concentrations and that the gene expression was significantly upregulated in tomato roots and leaves under 50 μM CdCl2 treatment. The pCAMBIA2300-SlSGR2 overexpression constructs were introduced into wild-type Arabidopsis plants via Agrobacterium-mediated transformation. Homozygous mutant lines of sgr2 were identified using the three-primer method. The growth of SlSGR2-overexpressed lines under Cd stress was significantly better than that of WT and sgr2. The chlorophyll, SOD, POD, and CAT contents of OE4-1 and OE4-2 were significantly higher than those of WT and sgr2 while the MDA content was significantly lower than other lines under cadmium stress. This study showed that the SlSGR2 gene is involved in Cd-induced plant senescence and is a negative regulator of plant chlorophyll degradation.

MdSGR2 Negatively Regulates Chlorophyll Degradation in Apple

“…The prediction of subcellular localization showed the probability of this protein being located in mitochondria. This is inconsistent with the results of previous studies on the subcellular localization of the SGR protein in tomatoes [46], Zoysia japonica [47], rice [25] and Tribulus terrestris alfalfa [48]. Therefore, we further confirmed the subcellular localization of MdSGR2 by fusion reporter gene analysis.…”

“…However, in this study, we found that MdSGR2 negatively regulates chlorophyll degradation. The function of MdSGR2 is consistent with that of SGR2 studied by Ma et al [46] in tomatoes and by Sakuraba et al [20] in Arabidopsis. Sakuraba et al [20] overexpressed the SGR2 gene in Arabidopsis and found that the plants showed an evergreen phenotype, and the sgr2-1 knockout mutant had advanced leaf yellowing under natural aging.…”

“…A GFP expression vector of MdSGR2 was constructed and expressed instantaneously in tobacco. Confocal laser microscopy showed that MdSGR2 is localized in chloroplasts, which is consistent with the subcellular localization of the SGR protein in tomatoes [46], rice [25], Arabidopsis [26], Zoysia japonica [47], and Medicago terrestris [45]. This result not only proves the properties of MdSGR2, but also provides instructions for subsequent experiments.…”