Abstract:

As conserved sequences of Arabidopsis CR4 protein，RCC1（PF00415），TNFR_c6 （PF00020）and Pkinase（PF00069）domains were used to search for the receptor like kinase CRINKLY4（CR4）genes in apple. The physical and chemical characteristics，evolutionary relationship and chromosomal distribution were analyzed for all of the identified CR4 genes. Additionally，tissue-specific expression profiles of CR4s were examined. Stress-specific expression of CR4s was determined in flower buds treated with lower temperature and trunks infected with Valsa mali. In total，eight CR4 genes were identified in the apple（Malus × domestica Borkh.）genome. The size（amino acid，AA），molecular weight and isoelectric point of apple CR4s varied from 668 to 1 690，from 71.73 to 187.61 kD and from 5.69 to 8.66，respectively. The expressed proteins were mainly sublocalized at plasma membrane（PM）. According to the phylogenetic analysis，apple CR4s could be divided into two sub-groups. Gene expression analysis showed that CR4s were distinctly expressed in different tissues and varieties. In addition，expression levels of eight and six CR4s were significantly changed at least in one time point when the flower bud under low temperature or the trunk was infected with Valsa mali，respectively. Among these，expression of MD03G1068800 was up-regulated more than 25 folds after the bud suffering low temperature，while that of MD00G1166500 and MD01G1153100 was up-regulated over 150 folds by Valsa mali，suggesting that these three CR4s can serve as candidate genes for further functional charaterization. This study sheds new light on future functional research of apple CR4s and provides new targets for stress-control and disease resistance regulation in apple industry.

Key words: apple, CR4, bioinformatic analysis, low temperature, apple canker, expression