Characterization of miRNAs responsive to exogenous ethylene in grapevine berries at whole genome level.

MicroRNAs (miRNAs) are critical regulators of various biological and metabolic processes of plants. Numerous miRNAs and their functions have been identified and analyzed in many plants. However, till now, the involvement of miRNAs in the response of grapevine berries to ethylene has not been reported yet. Here, Solexa technology was employed to deeply sequence small RNA libraries constructed from grapevine berries treated with and without ethylene. A total of 124 known and 78 novel miRNAs were identified. Among these miRNAs, 162 miRNAs were clearly responsive to ethylene, with 55 downregulated, 59 upregulated, and 14 unchanged miRNAs detected only in the control. The other 35 miRNAs responsive to ethylene were induced by ethylene and detected only in the ethylene-treated grapevine materials. Expression analysis of 27 conserved and 26 novel miRNAs revealed that 13 conserved and 18 novel ones were regulated by ethylene during the whole development of grapevine berries. High-throughput sequencing and qRT-PCR assays revealed consistent results on the expression results of ethylene-responsive miRNAs. Moreover, 90 target genes for 34 novel miRNAs were predicted, most of which were involved in responses to various stresses, especially like exogenous ethylene treatment. The identified miRNAs may be mainly involved in grapevine berry development and response to various environmental conditions.