Sucrose synthase (SUS) plays an important role in carbohydrate metabolism in plants. The SUS genes in licorice remain unknown. To reveal the sucrose metabolic pathway in licorice, all the 12 putative SUS genes of Glycyrrhiza uralensis were systematically identified by genome mining, and two novel SUSs (GuSUS1 and GuSUS2) were isolated and characterized for the first time. Furthermore, we found that the flexible N-terminus was responsible for the low stability of plant SUSs, and deletion of redundant N-terminus improved the stability of GuSUS1 and GuSUS2. The half-life of both GuSUS1 and GuSUS2 mutants was increased by 2-fold. Finally, the GuSUS1 mutant was coupled with UGT73C11 for the glycosylation of glycyrrhetinic acid (GA) with uridine 5′-diphosphate disodium salt hydrate (UDP) in situ recycling, and GA conversion was increased by 7-fold. Our study not only identified the SUS genes in licorice but also provided a stable SUS mutant for the construction of an efficient UDP-recycling system for GA glycosylation.

ABA has been found to play a significant role in post-embryonic developmental in peanut seedlings. The results from the current study indicate that in the presence of exogenous 10 lmol l -1 ABA, lateral roots (LRs) number decreased and seedling development was delayed. This effect was eliminated by 25 lmol l -1 naproxen, an inhibitor of ABA biosynthesis. The Arabidopsis mutant deficient in ABA biosynthesis, nced3, displays a phenotype with more and longer LRs. We found that ABA decreased rootbranching in peanut in a dose-dependent way. ABA-treated seedlings showed higher endogenous ABA levels than the control and naproxen-treated seedlings. RT-PCR results indicated that the expression of AhNCED1, a key gene in the ABA biosynthetic pathway, was significantly up-regulated by exogenous ABA in peanut. The mRNA levels of AhNCED1 began to increase 2 days after ABA treatment. The results from the current study show that ABA inhibits peanut LR development by increasing endogenous ABA contents.

No abstract

No abstract

A glutathione S-transferase (GST) gene cloned from the lepidopteran spruce budworm, Choristoneura fumiferana Clem. was transformed into the model plant Arabidopsis thaliana. The CfGST-transgenic and wild-type A. thaliana were subjected to 4 and 10 °C for 48 h and their cold resistance was studied. The GST activity of the transgenic plants was 46.6 and 35.7 % higher than that of the wild-type plants after 48 h under 4 and 10 °C, respectively. Relative membrane permeability and malondialdehyde content in the transgenic plants were lower while contents of the chlorophyll and proline were higher than those in the wild-type plants under 4 and 10 °C. The survival rate of the transgenic plants was 43.7 % for 24 h under 0 °C, while survival rate of wild-type plants was 28.3 %. The results indicated that the insect GST could enhance cold resistance in the transgenic A. thaliana.