‘南果梨’果实发育过程中糖分积累与相关基因表达分析

Sugar accumulation and expression of related genes in ‘Nanguo' pear fruit

【目的】探讨‘南果梨’果实发育过程中糖分变化与糖代谢相关基因表达之间的关系。【方法】以‘南果梨’不同发育时期的果实为试材,测定了其中果糖、葡萄糖、山梨醇和蔗糖的含量并分析了与糖代谢相关基因的表达。【结果】在果实幼果期山梨醇为主要糖,而在中后期则为果糖。蔗糖合成酶Pu SS1在花后60 d表达量最大,而Pu SS2在花后60、120及134 d表达量相对较高;蔗糖磷酸合成酶Pu SPS1在花后120 d的表达量最大,而Pu SPS2在花后60 d表达量最大;蔗糖转运蛋白Pu SUT及β-葡萄糖甘酶Pu BGLU1、Pu BGLU2和Pu BGLU4在果实发育的早期大量表达;碱性/中性转化酶Pu NINV1和Pu NINV2在花后134 d大量表达。【结论】各糖分在果实发育过程中变化规律不同,可能与糖代谢相关基因的差异表达有关。

【Objective】The metabolism of sugars affects fruit growth and development,and the accumulation of sugars in fruit is essential for quality formation.However,our understanding of gene expression involved in sugar metabolism and accumulation in pear fruit is quite limited.The purpose of this study is to analyze the variation of the major soluble sugars in‘Nanguo’pear(Pyrus ussuriensis Maxim.)fruit and their relationship with sugar metabolism-related gene expression during fruit development.【Methods】The contents of the major soluble sugars such as fructose,glucose,sorbitol and sucrose were measured by high performance liquid chromatography(HPLC).The expressions of related genes were measured by q-RTPCR(quantitative reverse-transcription PCR).【Results】About 60 days after full bloom(DAFB),sorbitol was the main component of sugars,while fructose accumulated rapidly from around 90 DAFB and became higher than glucose,sorbitol and sucrose at 134 DAFB.The content of sucrose was low at 60 DAFB,while the expression of sucrose phosphate synthase(SPS)genes(Pu SPS1 and Pu SPS2),sucrose synthase(SS)gene(Pu SS2),and sucrose transporter(SUT)gene(Pu SUT),which were genes responsible for sucrose synthesis and transport,were high.The low sucrose content might be caused by the high expression of Pu SS1,which decompose the sucrose for pear fruit growth.Sucrose had increased by 120 DAFB and the expression of Pu SPS1 and Pu SS2 also increased,indicating that the genes were important for the accumulationof sucrose.Neutral invertase(NINV)genes(Pu NINV1,Pu NINV2)were highly expressed at 134 DAFB,suggesting that the genes might be in charge of the decomposition of sucrose at the late stages of fruit development.Pu SUT had high expression levels at 60 DAFB and 90 DAFB and might be responsible for transport of sucrose at the early stage of fruit development.Glucose accumulated quickly at 60 DAFB and90 DAFB,and beta glucosidase(BGLU)genes(Pu BGLU1,Pu BGLU2 and Pu BGLU4 were also highly expressed at the same time,indicating that beta-glucosidase might be regulated to the accumulation of glucose【.Conclusion】The main results showed that sugar contents increased continually during fruit development,but they had different variation patterns.During the development of pear fruit,the different expression of sugar metabolism-related genes might play important roles in the variation of sugar composition.The analysis of the genes involved in sugar metabolism and accumulation in pear presented in this study provide a pioneer work for future studies on the functions of these genes.