MicroRNA319 family members play an important role in Solanum habrochaites and S. lycopersicum responses to chilling and heat stresses

The microRNA319 (miR319) family is involved in plant development and responses to abiotic stresses. Previous work showed that miR319 responded to chilling stress in the chilling-tolerant wild tomato (Solanum habrochaites L.) genotype LA1777. Here, the precursors of sha-miR319a, b, c, and d were cloned from LA1777 and the putative target genes tosinte branched/cycloidea/proliferating cell factors (TCP3 and TCP29) were validated using 5′-RLM-RACE. Expression patterns revealed a negative correlation of sha-miR319 with TCP3 and TCP29 in LA1777. Four tomato (S. lycopersicum) genotypes with varying sensitivities to chilling and heat stresses were selected to characterize expression patterns of miR319 and target genes under extreme temperatures. The involvement of miR319 in the chilling tolerance of tomato might be mediated by the repression of TCP3 and TCP29 expression. Initial stages of heat stress resulted in the up-regulation of miR319a, b, and d and led to a decrease in TCP3, TCP29, and TCP2 expression, whereas the down-regulation of miR319c in the later stages of heat stress may have been responsible for the subsequent up-regulation of TCP3, TCP29, and TCP2. Cis-elements found in the promoter regions of the miR319 family members indicated a potential role of miR319 in the regulation of stress tolerance and development processes. This study provides insights into the role of miR319-mediated regulatory mechanisms in responses to temperature stress in tomato genotypes.