In this study, we used virus-mediated gene silencing technology and found that the HSP17.4 gene-silenced cultivar Sweet Charlie plants were more susceptible to Colletotrichum gloeosporioides than the wild-type Sweet Charlie, and the level of infection was even higher than that of the susceptible cultivar Benihopp. The results of differential quantitative proteomics showed that after infection with the pathogen, the expression of the downstream response genes NPR1 , TGA , and PR-1 of the salicylic acid (SA) signalling pathway was fully up-regulated in the wild-type Sweet Charlie, and the expression of the core transcription factor MYC2 of the jasmonic acid (JA) pathway was significantly down-regulated. The expression of the proteins encoded by these genes did not change significantly in the HSP17.4 -silenced Sweet Charlie, indicating that the expression of HSP17.4 activated the up-regulation of downstream signals of SA and inhibited the JA signal pathway. The experiments that used SA, methyl jasmonate, and their inhibitors to treat plants provide additional evidence that the antagonism between SA and JA regulates the resistance of strawberry plants to C . gloeosporioides .
Background 7-dehydrocholesterol (7-DHC) can be directly converted to vitamin D 3 by UV irradiation and d e novo synthesis of 7-DHC in engineered Saccharomyces cerevisiae has been recognized as an attractive substitution to traditional chemical synthesis. Introduction of sterol extracellular transport pathway for the secretory production of 7-DHC is a promising approach to achieve higher titer and simplify the downstream purification processing. Methods and results A series of genes involved in ergosterol pathway were combined reinforced and reengineered in S. cerevisiae . A Biphasic fermentation system was introduced and 7-DHC was found to be enriched in oil-phase with an increased titer by 1.5-folds. Quantitative PCR revealed that say1, atf2, pdr5, pry1-3 involved in sterol storage and transport were all significantly induced in sterol overproduced strain. To enhance the secretion capacity, lipid transporters of Pry (Pathogen-related yeast proteins), NPC2(Niemann-Pick disease type C2), ABC(ATP-binding cassette)-family and their homologues were screened. Both individual and synergetic overexpression of Pr-1 (Plant pathogenesis Related protein-1) and St1 (Sterol transport1) largely increased the de novo biosynthesis and secretory productivity of 7-DHC, and the final titer reached 28.2 mg/g with a secretion ratio of 41.4%, which was 26.5-folds higher than the original strain. In addition, the cooperation between Pr-1 and St1 in sterol transport was further confirmed by confocal microscopy, molecular docking and directed site-mutation. Conclusion Selective secretion of different sterol intermediates was characterized in sterol over-produced strain and the extracellular export of 7-DHC developed in present study significantly improved the cell biosynthetic capacity, which offered a novel modification idea for 7-DHC de novo biosynthesis by S. cerevisiae cell factory. This article is protected by copyright. All rights reserved
危险品化学品经营许可证（带存储）