To further study the characteristics of peach codon usage, this study analyzed codon usage biases and codon usage patterns of peach genome, based on the statistical calculations of related GC content, effective number of codons (ENC) and relative synonymous codons (RSCU) from 26 873 coding sequences. The results showed that there were obvious biases in codon usage of peach, and 4 out of 61 codons (UCA, ACA, GCA and GAA) were defined as the optimal codons, all of which end with Adenine at the third codon position. Further analyses of codon usage frequency among peach and other 9 relative species in Rosaceae found that the codon usage patterns in the relative genus were similar. These results also suggested that there was a positive correlation between the copy number of tRNA genes and the occurrence frequency of corresponding amino acids (and specific codons) in the peach genome. These results revealed codon usage patterns in Peach and provide an important reference for the relevant studies on codon usage mechanism and the genetic engineering.

桃(Prunus persica)是我国重要的经济果树,对农业经济的发展具有重要作用.低温影响桃树生长发育,是桃早春生产的威胁之一.为探究亚热带地区桃树的低温适应及冷驯化机制,本研究对比分析了 4℃48 h低温处理后桃树低需冷量种质'MX14-1'叶片转录表达谱的变化,差异表达基因的GO功能注释和KEGG通路功能富集分析显示,低温胁迫下桃树叶片差异表达基因主要与胁迫应答相关,富集于次生代谢物合成途径,涉及类黄酮、芪类、二苯基庚酮、姜酚和苯丙烷合成、亚油酸代谢等途径.利用qRT-PCR技术对类黄酮代谢相关基因进行分析,结果显示4℃48 h处理后,苯丙氨酸解氨酶(phenylalanine ammonialyase,PAL)、肉桂酸4-羟酶(cinnamic acid 4-hydroxylase,C4H)、4-香豆酸辅酶 A 连接酶(4-coumarate:CoA ligase,4CL)、查尔酮合酶(chalcone synthase,CHS)、查尔酮异构酶(chalcone isomerase,CHI)、类黄酮-3-羟化酶(flavanone 3-hydroxylase,F3H)基因表达显著上调,和转录组测序结果一致.叶片代谢物含量测定表明,低温胁迫桃树叶片中类黄酮代谢相关的黄酮醇及衍生物含量显著增加.4℃48 h处理组和对照同时进行-2℃冷冻处理,结果表明经4℃低温处理桃树叶片中类黄酮物质总量和抗氧化能力显著提高,-2℃冷冻处理时损伤降低.本研究可为进一步探究桃树低温响应与抗寒的分子机制提供参考.

桃果实解袋后使用山梨醇溶液进行喷施,研究采摘果实中类黄酮、类胡萝卜素含量变化.测定结果表明,成熟桃果肉中类黄酮化合物总含量显著提高;类胡萝卜素物质总含量不同程度下降.QPCR定量结果显示类黄酮合成通路前期阶段关键基因PAL、CHS、CHI表达增强,类胡萝卜素合成通路前期阶段关键基因PSY、ZDS转录表达减弱.果实解袋后喷施山梨醇可影响成熟期果实中类黄酮、类胡萝卜素物质的合成与积累水平.

[目的]了解喷施山梨醇及其类似物对桃叶片、果实中钾、钠、钙运输积累和对内源激素含量的影响.[方法]使用山梨醇及其结构类似的糖醇类渗透调节物(甘露醇、异山梨醇)喷施桃树体,测定桃叶、桃果实中的钠、钾、钙含量以及内源植物激素含量变化.基于测定结果,Q-PCR检测桃叶、桃幼果中相关离子转运子与特定激素合成通路关键限速酶基因的表达.[结果]喷施处理组中,果实钠、钾、钙含量显著增加(其中异山梨醇处理组中果实钠、钾、钙含量增加的幅度最大);但叶片中钠、钾、钙变化不显著.Q-PCR检测表明:钠离子转运相关的PpNHX7/SOS1在处理组叶片、果实中表达增强.钾离子转运相关的PpKUPs、PpKEAs在处理组叶片中表达趋势增强,在果实中PpKUPs表达增强、PpKEAs表达减弱.此外,喷施处理组中,桃果实内源性玉米素含量升高,玉米素合成通路关键限速酶基因PpIPT和PpCYP735A表达上调.[结论]山梨醇及其类似物喷施可能造成渗透胁迫,促使果实积累钠、钾、钙,并促进玉米素的合成以响应胁迫.

[目的]研究外源山梨醇对桃叶片基因表达网络的影响.[方法]采用100 mg·L-1山梨醇溶液喷施桃幼苗,以清水喷施为对照.转录组测序,分析山梨醇处理样品中成熟叶(喷施山梨醇)和幼叶中(未喷施山梨醇)相关基因表达的变化.[结果]转录组测序表明,成熟叶(喷施山梨醇)中差异表达的基因数多于幼叶(未喷施山梨醇).成熟叶中与胁迫相关的基因表达上调,次级代谢物代谢通路发生变化.幼叶中碳水化合物代谢相关基因表达发生改变.一些与环境应激相关的基因在成熟叶和幼叶中表达均上调,与离子平衡、细胞内脂质代谢相关的一些基因表达均下调.[结论]山梨醇喷施后,成熟叶中胁迫响应机制启动,影响次级产物代谢.当相关信号传递到幼叶后,碳水化合物代谢平衡发生相应变化,响应相关刺激.基本明确了桃对高浓度外源山梨醇溶液喷施的响应过程及涉及的代谢通路.

Genetic diversity of 50 Prunus persica germplasms was analyzed using 16 pairs of SSR primers.The results showed that the polymorphism information contents of the individual sites ranged from 0.04 to 0.37 with an average of 0.24.The 50 peach germplasms could be classified into 3 groups according to thecluster analysis of the unweighted pair group method witharithmetic mean.They were medium late-maturing,medium early-maturing and low-temp early-maturing peaches.In addition,the low-temp germplasms with excellent over-all properties in the hot and humid southern regions could be grouped by themselves.The ornamental varieties were genetically far remote from the common peaches.A genetic analysis indicated that some of the local germplasms found in Fujian were typical southern peaches.Thus,from the molecular level,it confirmed the previous understanding of the origin of local varieties to be south of the Yangtze River.