Expression of miRNAs and their target genes in roots of 'Sanhu' tangerine (Citrus reticulata blanco cv. 'Sanhu') in response to Candidatus Liberibacter asiaticus infection.

MicroRNA (miRNA) profiles were studied in roots of 'Sanhu' tangerine plants with and without Candidatus Liberibacter asiaticus (CLas) infections by using solexa sequencing to investigate the possible involvement of miRNAs in the pathogenesis of Citrus Greening (Huanglongbing) disease. A total of 186 known miRNAs and 71 novel miRNAs were thus identified. Of them, 37 known and 18 novel miRNAs were significantly different in their expression patterns in roots of CLas-free and CLas-infected plants. CLas infection induced de novo expression of 6 known miRNAs and up-regulated the expression of 13 known miRNAs. It also prevented the expression of 11 known miRNAs and down-regulated the expression of 7 others. A total of 316 genes were predicted to be the targets of these differentially expressed miRNAs. Particularly, 34, 28, 21, and 20 genes were predicted to be the respective targets of cre-miR156a, cre-miR396b, cre-miR396g-5p, and cre-miRn70. The predicted putative target genes are known to be involved in stress response, plant growth and development, transcription, and metabolism. Quantitative analyses of the expression of several representative miRNAs and their target genes were generally in agreement with the predicted expression patterns (inverse proportion). Further research to unravel the interactions between these miRNAs and their target genes and determine the associated biological and pathological significance is recommended. [ABSTRACT FROM AUTHOR]