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摘 要 以10年生‘砂糖橘’（Citrus reticulata Blanco）為对象，研究夏梢生长对幼果及果柄离区的细胞壁降解酶活性、相关基因表达及其脱落的影响。结果表明：夏梢萌发6 d后幼果大量脱落，15 d后累积落果率高达79.5%，比同期去梢的增加91.7%。夏梢生长明显促进幼果和离区中纤维素酶（Cx）、多聚半乳糖醛酸酶（PG）活性的提高，其活性水平与相对落果率均达显著正相关。果胶（甲）酯酶（PME）、β-半乳糖苷酶（β-Gal）活性不受夏梢生长所影响。基因表达结果显示，夏梢生长促进CsPG、Csβ-Gal和CsCx的表达上调，6 d时出现表达峰值，而CsPME的表达不受夏梢影响。综合认为‘砂糖橘’夏梢生长诱导幼果脱离过程中，Cx、PG是参与脱落调控的细胞壁降解关键酶。
关键词 砂糖橘；夏梢；细胞壁降解酶；基因表达；脱落
中图分类号 S666.2 文献标识码 A
Effects of Summer Shoot Growth on Activities and Gene Expression
of the Cell Wall Degradation Enzymes in‘Shatangju’
Mandarin Fruitlet and Abscission Zone
HUANG Yongjing1，2， CHEN Jiezhong2 *， ZENG Jiwu1， WU Wen1 *，
ZHANG Ruimin1， ZHU Congyi1
1 Institute of Fruit Tree Research， Guangdong Academy of Agricultural Sciences / Key Laboratory of South Subtropical
Fruit Biology and Genetic Resource Utilization， Ministry of Agriculture， Guangzhou， Guangdong 510640， China
2 College of Horticulture， South China Agricultural University， Guangzhou， Guangdong 510642， China
Abstract The objective of this work was to investigate the effects of shoot growth on the activities， gene expression of the cell wall degradation enzymes and abscission of fruitlet and abscission zone（AZ）in Citrus. 10-year old trees of‘Shatangju’mandarin（Citrus reticulata Blanco）were used as the material. The results showed that summer shoot obviously increased fruitlet abscission. At the 15th day， the accumulative abscission rate（AAR）in shoot-retained treatment was 79.5%， which was 91.7% higher than that in shoot-removed treatment. Moreover， the activities of cellulase（Cx）and polygalacturonase（PG）in fruitlet and AZ were dramatically increased during the summer shoot growth， and the activities of those two enzymes were positively correlated with the relative abscission rate（RAR）. However， the activities of pectin methylesterase（PME）and β-galactosidase（β-Gal）were not influenced by summer shoot growth. qRT-PCR analysis showed that the expression levels of CsPG， Csβ-Gal and CsCx were significantly upregulated during the summer shoot growth， with the expression peaks were appeared at the 6th day， but a little effect was found in the expression of CsPME. These results suggested that during fruitlet abscission induced by summer shoot growth in‘Shatangju’mandarin， Cx and PG were the key cell wall degradation enzymes which regulated fruitet abscission.
Key words Shatangju； summer shoot； cell wall degradation enzymes； gene expression； abscission