Transcription factor PbMYB80 regulates lignification of stone cells and undergoes RING finger protein PbRHY1-mediated degradation in pear fruit.

The Chinese white pear (Pyrus bretschneideri) fruit carries a high proportion of stone cells, adversely affecting fruit quality. Lignin is a main component of stone cells in pear fruit. In this study, we discovered that a pear MYB transcription factor, PbMYB80, binds to the promoters of key lignin biosynthesis genes and inhibits their expression. Stable overexpression of PbMYB80 in Arabidopsis showed that lignin deposition and secondary wall thickening were inhibited, and the expression of the lignin biosynthesis genes in transgenic Arabidopsis was decreased. Transient overexpression of PbMYB80 in pear fruit inhibited lignin metabolism and stone cell development, and the expression of some genes in the lignin metabolism pathway was reduced. In contrast, silencing PbMYB80 with VIGS increased the lignin and stone cell content in pear fruit, and increased expression of genes in the lignin metabolism pathway. By screening a pear fruit cDNA library in yeast, we found that PbMYB80 binds to a RING finger (PbRHY1) protein. We also showed that PbRHY1 exhibits E3 ubiquitin ligase activity and degrades ubiquitinated PbMYB80 in vivo and in vitro. This investigation contributes to a better understanding of the regulation of lignin biosynthesis in pear fruit, and provides a theoretical foundation for increasing pear fruit quality at the molecular level.

[Comparison of effectiveness between two HIV screening strategies in outpatient setting].

OBJECTIVE: To determine whether non-targeted testing strategy (screening all patients with blood sample withdrawn) could identify more patients with newly diagnosed HIV infection than symptom and risk behavior based targeted testing strategy or not. METHODS: Controlled trial design was applied in this study.From July to November 2011, outpatient department of L and J county hospital in Guangxi province were selected to conduct the targeted strategy and non-targeted strategy respectively. The two counties had similar population, outpatient volume, previous testing rate and number of newly identified HIV cases.Outpatients older than 15 years were recruited as study subjects, with 62 106 person time in L hospital and 58 257 in J hospital. Data about visit number, persons receiving HIV testing and HIV positive cases were collected by outpatient department. Chi-square test was used to compare the percentage of newly identified HIV cases, HIV positive detection rate and proportion of cases in early AIDS phase between two strategies. RESULTS: During the study period, 9.69% (5627/58 057) of all outpatients in J hospital with non-targeted strategy and 1.38% (859/62 106) of all outpatients in L hospital with targeted strategy received HIV test. The average age of patients receiving HIV testing was 46.23 ± 16.81 and 40.75 ± 15.48 respectively, which was statistically different (t = 8.81, P < 0.05). The percentage of newly identified HIV cases was significantly greater in J hospital (0.03% (19/58 057)) than that in L hospital (0.02% (10/62106)) (P < 0.05) while the HIV positive detection rate was lower in J hospital (0.34% (19/5627)) than that in L hospital (1.16% (10/859)) (χ(2) = 9.66, P < 0.05). CONCLUSION: In a concentrated epidemic, a hospital based non-targeted strategy could detect more unidentified HIV cases than targeted strategy.