Identification and Expression Profiling of miRNAs and siRNAs in Chilled Vegetative Buds and Non-chilled Leaf Tissue in Peach

Chilling requirement is the absolute requirement for sustained exposure to low, near freezing, temperatures before resumption of active bud break and shoot growth following winter period. Chilling requirement decreases the risk of frost damage of flower and leaves by fluctuating temperatures in the springtime. Peach genotypes present a wide range of chilling hours ranging from  less than 50 to 1100 hours. Recent studies in Arabidopsis showed that vernalization, which superficially resembles chilling requirement, is epigenetically regulated. Comparative studies could shed light on molecular mechanisms involved in this process in trees. However, little is known on the genic nature of chilling requirement, which is different from vernalization and may involve different or modified gene regulatory networks. To identify key siRNA epigenetic signatures associated with chilling requirement in peach, we sequenced small RNA transcitpomes from chilled vegetative buds and young leaves using SOLID platform. In silico expression analyses of small RNAs in chilled versus non chilled tissues is in process of being analyzed. siRNAs differentially expressed in chilled versus non-chilled tissues will be identified and their targets predicted. siRNA targets will be compared to candidate genes from Arabidopsis and tested for co-localization with peach QTLs for chilling requirement that were previously identified. Results from this work will be the subject of this presentation.