miRNAs involved in transcriptome remodeling during pollen development and heat stress response in Solanum lycopersicum

Cellular transitions during development or in response to environmental changes depend on coordinated transcriptomic and proteomic alterations. Pollen are particular as they are a very heat sensitive and their development is a dynamic process that includes meiotic and mitotic divisions. Both, stress response and development are accompanied by a timely reprogramming of the transcriptome, e.g. by post-transcriptional regulation by miRNAs. On the example of Solanum lycopersicum (tomato), which has been extensively used as model system for plant stress responses, we identified miRNAs likely involved in post-transcriptional regulation of the transcriptome of pollen. Somewhat different to observations for other tissues, an equal abundance of CDS and 3'UTR targeting miRNAs has been observed. We describe a link between miRNAs and the abundance of mRNAs coding for transcription factors during development. In addition, some of the identified miRNAs are likely involved in the proposed developmental priming, which is thought to protect pollen against damages enforced by sudden environmental alterations. These miRNAs target transcripts coding for transcription factors or other proteins involved in the regulation of cellular homeostasis under stress. Thus, we provide evidence for a tight integration of miRNA based regulation into the molecular network for pollen development and heat stress response.