ABSTRACT
In this study, 13 xyloglucan endotransglycosylases/hydrolases (XTHs) and 8 expansin (EXPs) were screened from safflower floret transcriptome database. Through correlation analysis between the safflower gene expression profile chip and the corolla development, only 4 XTHs (CtXTH1-4) and 1 EXP (CtEXP1) have positive relevance with corolla elongation (r≥0.60) and were therefore validated by qRT-PCR. The full length of these genes were cloned by RACE. According to the bioinformatic analysis, CtXTH1 correlated with the development of the floret, and the expression pattern analysis indicated that CtXTH1 had accumulated in the floret. The recombinant vector (pMT39-CtXTH1) was constructed for gene transformation. Overexpression of CtXTH1 significantly increased the corolla length (about 5.34% to 10.25%) and corolla weight (about 30.00% to 36.02%) in transgenic safflower. The overexpression lines also showed an increasing tendency in the weight of seeds, average number of corollas per cone and average number of seeds in each cone. Meanwhile, overexpression of CtXTH1 had no significant effect on flavonoids. According to the corolla microstructure, the OVX-line tubular part of floret exhibited a looser and irregular character. These data suggested that CtXTH1 can potentially increase relaxation of the tissues and boost corolla elongation. Our study provides a valuable clue for plant breeding in the future.
ABSTRACT
Flavonoids, especially chalcones such as hydroxysafflor yellow A and carthamin are the main active ingredients of safflower. To study the biosynthesis pathway of safflower flavonoids is of great significance for the quality control of safflower. Chalcone synthase (CHS) is an enzyme that plays an important role in regulation of the synthesis of flavonoids. However, for the time being, the role of CHS is not yet clear in the biosynthesis of safflower flavonoids. As a plant signaling regulator, JA/MeJA can activate CHS gene expression in plants. CtCHS1, one of the CHS genes in safflower, was elucidated in our previous work. In our continuous search for CtCHSs functions from this plant, other CHS genes CtCHS2 and CtCHS4 in safflower were examined. The floret was stimulated with methyl jasmonate (MeJA) and the transcriptome expression of CtCHS2 and CtCHS4 was analyzed by qRT-PCR at different time points of 0, 3, 6, and 12 h after stimulation. Further metabolites under stimulation by MeJA were analyzed by UHPLC/Q-TOF-MS. The results showed that the expression of CtCHS4 in response to MeJA significantly increased at 3 and 6 h, while the expression of CtCHS2 showed a trend of decrease after induction. Meanwhile, the accumulation of rutin, hydroxysafflor yellow A, D-phenylalanine, kaempferol-3-O-β-rutinoside and carthamin increased obviously. Especially, accumulation of hydroxysafflor yellow A was increased significantly at 3, 6 and 12 h after induction (P ≥ 0.05 or 0.01), but the change in kaempferol, kaempferol-3-O-β-D-glucoside, luteolin, quercetin-3-β-D-glucoside was not significant. The accumulation of hydroxysafflor yellow A and carthamin was positively correlated with the expression abundance of CtCHS4 with Pearson correlation analysis method (r ≥ 0.8). The data suggest that CtCHS4 may be a key gene for forming hydroxysafflor yellow A and carthamin and plays an important role in the accumulation of safflower chalcones. The CtCHS4-pMAL-C5X recombinant vector was successfully expressed in BL21 (DE3) Plys to express the product naringenin in vitro under the catalytic substrates p-coumaryol-COA and malonyl-CoA. The results of this study provide a new insight into synthetic genes involved in flavonoids biosynthetic pathway to elucidate the biosynthesis pathway of safflower chalcones.
ABSTRACT
As a secondary metabolite in plant, anthocyanins plays an important role in many aspects of plant life, and also exhibits various activities including the anti-oxidation, anti-inflammatory, antibacterial, antitumor and cardio-cerebral vascular protective in animals. They are a group of important natural drug candiadtes in the prevention of cardiovascular and cerebrovascular diseases and metabolic diseases. Therefore, exploration of the biosynthetic pathway and regulatory mechanism of anthocyanins is of great interest for improvement of anthocyanin production and development of low-cost production methods. Circadian clock, as a ubiquitous regulatory system in organisms, affects plant physiological and molecular processes, and also regulate the anthocyanin biosynthesis. To provide new ideas on anthocyanin biosynthesis, we provide a review of the recent progress in circadian rhythm clock with regard on regulation of anthocyanin biosynthesis in this paper.