关键词: 苹果, LRR-RLK, 基因家族, 鉴定, 表达分析

Abstract:

【Objective】 The study was carried out to explore the whole genome characteristics and expression patterns ofLRR-RLKs in apple, to reveal the expression specificity of family members in different tissues and their responses to biological and abiotic stress, and further understand its biological function in apple. 【Method】 The members of LRR-RLK gene family in the whole genome of apple were identified based on the local BLAST database and Pfam database. The LRR-RLK amino acid sequence prediction, subcellular localization prediction, domain analysis, phylogenetic tree and chromosome localization were completed by software of ExPASy Proteomics Server, Cell-PLoc, CD-Search Tool, MEGAX and MG2C. In addition, the expression pattern of 12 LRR-RLK genes in different tissues and stress were analyzed by real-time fluorescent quantitative PCR (qRT-PCR).【Result】 A total of 378 LRR-RLKgenes were identified from apple genome. TheseLRR-RLKgenes encoded proteins containing 318-1 827 amino acid, and the theoretical isoelectric point ranged from 6.14 to 9.01. The prediction subcellular localization of apple LRR-RLK proteins was all distributed in the cell membrane. The gene family could be divided into 15 subgroups, containing 1-111 genes. The 378 genes in this family were distributed on all 17 chromosomes of the apple, and the chromosome 7 contained 40 genes. The LRR-RLK gene family had two conserved domains, namely the leucine-rich repeat structure and the protein kinase domain. Irregular curl and α-helix was the main secondary structure in the LRR-RLK gene family, and the rotation of β-turn was very small. It was found that the 12 selected family members were expressed in all tissues (except MD00G1105400), and most genes were expressed at relatively high levels in stem. Seven genes were up-regulated under low temperature conditions, and the expression of MD09G1153800 was the most obvious. The expression of MD09G1153800 was raised to 6.8 times of that under the control. While MD06G1170200 and MD05G1061600 were both down-regulated. Eight genes were up-regulated under drought conditions, and MD00G1105400 was the most obvious one. The expression of MD00G1105400 was raised to 9.6 times of that under the control; under salt conditions, MD04G1150400, MD13G1108000 and MD02G1071800 were always up-regulated. Among them, MD02G1071800 had the highest expression after 24 hours of salt stress treatment, which was 14.9 times of that under the control. After inoculating Botryosphaeria dothidea, the expression of 12 LRR-RLKgenes increased first and then decreased. After inoculating, the expression level of Wangshanhong was higher on the first day, however the expression level of Jiguan was higher on the third day. The expression of MD09G1153800 and MD05G1065800 were up-regulated significantly in Jiguan, in relative to have no change in Wangshanhong, suggesting that these twoLRR-RLKscould serve as candidate genes for further functional characterization. 【Conclusion】 A total of 378 LRR-RLK members were identified from apple whole genome sequences, which could be divided into 15 groups and distributed on 17 chromosomes, and the most of LRR-RLK genes were responsive to stress stimulus and Botryosphaeria dothidea.

Key words: apple, LRR-RLK, gene family, identification, expression analysis