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The PcHY5 methylation is associated with anthocyanin biosynthesis and transport in ‘Max Red Bartlett’ and ‘Bartlett’ pears
WEI Wei-lin, JIANG Fu-dong, LIU Hai-nan, SUN Man-yi, LI Qing-yu, CHANG Wen-jing, LI Yuan-jun, LI Jia-ming, WU Jun
2023, 22 (11): 3256-3268.   DOI: 10.1016/j.jia.2023.07.017
Abstract204)      PDF in ScienceDirect      

The red coloring of pear fruits is mainly caused by anthocyanin accumulation.  Red sport, represented by the green pear cultivar ‘Bartlett’ (BL) and the red-skinned derivative ‘Max Red Bartlett’ (MRB), is an ideal material for studying the molecular mechanism of anthocyanin accumulation in pear.  Genetic analysis has previously revealed a quantitative trait locus (QTL) associated with red skin color in MRB.  However, the key gene in the QTL and the associated regulatory mechanism remain unknown.  In the present study, transcriptomic and methylomic analyses were performed using pear skin for comparisons between BL and MRB.  These analyses revealed differential PcHY5 DNA methylation levels between the two cultivars; MRB had lower PcHY5 methylation than BL during fruit development, and PcHY5 was more highly expressed in MRB than in BL.  These results indicated that PcHY5 is involved in the variations in skin color between BL and MRB.  We further used dual luciferase assays to verify that PcHY5 activates the promoters of the anthocyanin biosynthesis and transport genes PcUFGT, PcGST, PcMYB10 and PcMYB114, confirming that PcHY5 not only regulates anthocyanin biosynthesis but also anthocyanin transport.  Furthermore, we analyzed a key differentially methylated site between MRB and BL, and found that it was located in an intronic region of PcHY5.  The lower methylation levels in this PcHY5 intron in MRB were associated with red fruit color during development, whereas the higher methylation levels at the same site in BL were associated with green fruit color.  Based on the differential expression and methylation patterns in PcHY5 and gene functional verification, we hypothesize that PcHY5, which is regulated by methylation levels, affects anthocyanin biosynthesis and transport to cause the variations in skin color between BL and MRB.

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Molecular, serological and biological characterization of a novel Apple stem pitting virus strain from a local pear variety grown in China
LI Liu, ZHENG Meng-meng, MA Xiao-fang, LI Yuan-jun, LI Qing-yu, WANG Guo-ping, HONG Ni
2019, 18 (11): 2549-2560.   DOI: 10.1016/S2095-3119(19)62636-5
Abstract127)      PDF in ScienceDirect      
Apple stem pitting virus (ASPV) is an important causal agent of pear diseases.  Nowadays, the infection status and molecular characteristics of the virus in old pear trees have never been investigated.  In this study, we provide the first complete genome sequence of an ASPV isolate LYC from an over 300-year-old tree of a local Pyrus bretschneideri cultivar ‘Chili’ specifically grown at Laiyang area in China.  ASPV-LYC possesses a chimeric genome consisting of 9 273 nucleotides excluding a poly(A) tail at its 3´ end and harboring a recombination region in its open reading frame (ORF1) with Aurora-1 and KL9 identified as the major and minor parents.  Western blot analysis with antisera against recombinant coat proteins (CPs) of three ASPV isolates from pear indicates that ASPV-LYC is serologically related to these ASPV isolates, but with differential activities.  Further biological tests on indicator plants of Pyronia veitchii show that ASPV-LYC can induce serious leaf and stem symptoms as other ASPV isolates.  The results provide an important information for understanding molecular evolution of ASPV and suggest a need to prevent dissemination of the isolate among pear trees.
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