Ethylene Biosynthesis And Expression Of Related Genes In Loquat Fruit

Non-climacteric loquat fruit(Eriobotrya japonica Lindl. vc. Luoyangqing) was used to study ethylene biosynthesis and expression of related genes in fruit of different development stages and different posthavest storage conditions. The objective of the present study was to investigate the biological mechanisms of ethylene biosynthesis in regulating fruit development, ripening, senescence and abiotic stress of loquat fruit.According to the CCI of'Luoyangqing'loquat, fruit were divided into five developmental stages as follows:S1 (CCI<-9), S2 (CCI:-6～-4), S3 (CCI:-1～1, colour turning period), S4 (CCI:3-5), S5 (CCI:9-11) (harvest time). During fruit development, ethylene production and respiration rate showed similar patterns with a peack at S3 stage. After fruit was fully mature and harvested, ethylene production and respiration rate were very low and decreased during storage at 20℃, and both of them were even lower in fruit stored at 0℃.By using degenerate primers, three ethylene biosynthesis related genes, i.e. EjACS1, EjACO1, EjACO2 were cloned from'Luoyangqing'loquat. Amino acid sequences analysis showed that they had the highest idendities with PbACS2 (94%), MdACO1 (96%), PPACO1 (96%), respectively.Real-time quantitative PCR (Q-PCR) analysis was used for the gene expression in the present study. Expression of EjACS1 and EjACO1 showed fruit tissue specificity while high expression of EjACO2 could be detected in leave and flower as well. During fruit development, EjACS1 and EjACO1 showed high expression level at later stages while expression pattern of EjACO2 was consistent with the ethylene production during fruit development, reaching a peak at S3 when the fruit colour was turning. EjACSl, EjACO1 and EjACO2 had different expression during fruit storage under different conditions:the expressions of EjACSl and EjACO1 decreased during ripening at 20℃; EjACSl, EjACO1 and EjACO2 showed a stable expression level during low temperature (0℃) with the expression of EjACS1 and EjACO2 was higher than the control fruit; expressions of EjACS1, EjACO1 and EjACO2 decreased after fruit stored under low humidity for 6-8 d; mechanical injury induced the expression of EjACS1 and EjACO2, but had no apparent effect on EjACO1.It is the first time to study the gene expression of ethylene biosynthesis related genes in loquat fruit. Climacteric increases in ethylene production and respiration rate were observed during the development of loquat fruit and EjACO2 may play an important role in such a process. EjACS1, EjACO1 and EjACO2 showed different expression patterns in fruit of different storage conditions, where EjACS1 and EjACO2 had high consistency during fruit ripening and its response to low temperature, low humidity, and mechanical injury.