Screening Of Apple Ring Rot-Responsive Mirnas

miRNAs are endogenous non-coding small RNAs (sRNAs), typically18-25nucleotides (nt) in length, that regulate gene expression from messenger RNA (mRNA) by repressing gene translation or degrading target mRNAs. They have important regulatory roles in both plant and animal gene expression. In plants, miRNAs are involved in development, signal transduction, protein degradation and response to environmental stress and pathogen invasion. miRNAs also regulate their own biogenesis.Since the late seventies, cultivation of quality apple varieties that are sensitive to this disease has increased, resulting in a high incidence of apple rot that has become a significant problem in fruit production. Crabapple (M. hupenhensis) is commonly used for apple rootstocks and is resistant to fungal diseases like apple ring rot. Studies on crabapples will provide insight into the resistance mechanisms of apple ring rot stress and possibilities for increasing rot resistance in the Fuji cultivar. To understand the role of miRNAs in the response of apples to apple ring rot fungi, it is important to improve the resistance of Fuji.The major findings are as follows:1. By high-throughput sequencing we found165miRNA belonged to49miRNA families in Fuji stems. The targets of miRNA were predicted, and targets mostly encoded transcription protein, which was similar with other plants. In addition, we also predicted380new candidate miRNA, which were detected in leaves and stems of Fuji by semi-quantitative PCR. The expression of new candidate miRNA has organ specificity. In our study, we found the known miRNA and new candidate miRNA that play an important role in the growth of Fuji.2. By high-throughput sequencing we found165miRNA belonged to52miRNA families in Crabapple stems. The targets of miRNA were predicted, and targets mostly encoded transcription protein, which was similar with other plants. In addition, we also predicted821new candidate miRNA, which were detected in leaves and stems of Fuji by semi-quantitative PCR. The expression of new candidate miRNA was difference in leaves and stems and has organ specificity. In our study, we found the known miRNA and new candidate miRNA that play an important role in preservation, evalution and utilization of Crabapple.3. Comparison the miRNA of Fuji and Crabapple, which had differenf resistance to apple ring rot, we found that11miRNA were related to apple ring rot, the expression of9miRNA were up-gegulated, and the expression of2miRNA were down-regulated. Their targets were involved in stress and might be associated with apple ring rot. It was important to improve the apple ring rot resistance of Fuji.4. Comparison the miRNA of Fuji and Crabapple stems, which were infected by apple ring rot, we found that24miRNA were related to apple ring rot. The expression patterns of miRNA were identified by qRT-PCR. Moreover, we found that the expression of five miRNAs increased significantly at two time points (9h and24h) after apple ring rot treatment. Research showed that miRNA might play an important role to resistant apple ring rot.