中文摘要：

【目的】探究不同时期水分胁迫处理对椪柑果实有机酸含量及与柠檬酸代谢相关酶基因表达的影响。【方法】以6 a（年）生盆栽枳砧普通椪柑（Citrus reticulata Blanco）为试材,设全期、前中期、前期、中期、后期等5个处理,以正常浇水为对照。用HPLC测定果肉中酸的含量,用相对荧光定量PCR测定柠檬酸代谢相关基因的相对表达量。【结果】5个处理组均导致果实中柠檬酸、苹果酸、奎宁酸等3种有机酸及总酸浓度显著增加;Cit CS1与Cit CS2的相对表达量均出现不同程度上调;Cit Aco1的相对表达量总体是上调表达,Cit Aco2的相对表达量因不同时期处理而异,Cit Aco3的相对表达量出现不同程度下降;Cit IDH2在3个Cit IDH基因中相对表达量最低,但其表达均得到促进,Cit IDH1的相对表达量因不同时期而异,而对Cit IDH3而言,其相对表达量总体是抑制表达;2个Cit GAD基因中,Cit GAD5启动较早,水分胁迫下Cit GAD4、Cit GAD5的表达均受到抑制,Cit GAD5所受影响更为显著。【结论】不同时期水分胁迫能导致椪柑果实柠檬酸积累,总有机酸含量升高,这种变化与柠檬酸代谢相关基因表达量发生变动有关。其中,Cit CS1、Cit CS2表达上调及Cit Aco3、Cit IDH3、Cit GAD4和Cit GAD5表达下调可能是果实柠檬酸积累的原因之一。

英文摘要：

【Objective】To explore the influence of water stress within different development stage on or-ganic acid content and gene expression related to citrate metabolism in Ponkan fruit.【Methods】With 6-year potted trifoliate orange common Ponkan（Citrus reticulata Blanco）trees as test materials,regular wa-tering as control,five treatments along with the fruit growth process were arranged,including the wholeperiod,the earlier stage,the premetaphase stage,the medium-term stage and the later stage. The contentof acids in fruit were determined by HPLC,and relative expression of genes related to citric acid metabol-ic were determined by relative fluorescence quantitative PCR.【Results】Five treatment groups under wa-ter stress led to citric acid,malic acid,quinic acid and total acid concentration increased significantly.Relative expressions of Cit CS1 and Cit CS2 had all been raised to a certain extent. The relative expressionof Cit Aco1 was higher in overall,and relative expression of Cit Aco2 varied in different periods of treat-ments. However,relative expression of Cit Aco3 was declined to varying degrees. Relative expression of Cit IDH2 was the lowest in the three Cit IDH genes,but its all expression got the promotion. Relative ex-pression of Cit IDH1 varied under different treatment stage. The expression of Cit IDH3 was inhibited over-all. For the 2 Cit GAD genes,Cit GAD5 was activated earlier,the expressions of Cit GAD4,Cit GAD5 were inhibited under water stress at the different periods of treatment,the impact to Cit GAD5 was more signifi-cant.【Conclusion】Water stress within different development stages caused the accumulation of citric ac-id,increased total organic acid content,these changes were related to the changes of the relative expres-sions of genes telated to citric acid synthesis and degradation in the ponkan fruit. The down-regulation of Cit Aco3,Cit IDH3,Cit GAD4 and Cit GAD5 and up-regulation of Cit CS1,Cit CS2 might be one of the rea-sons why citric acid accumulated.