Functional role of miR159/SlyGAMYB1 during fruit set in tomato (Solanum lycopersicum L.)

Author(s)

Eder Marques da Silva

• Document type: Doctoral Thesis
• Press: Botucatu. 2016-05-25.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu
• Defense date: 2016-05-19
• Advisor: Fábio Tebaldi Silveira Nogueira

Abstract

Fruit set, defined as the shift from quiescent ovary to a fast-growing young fruit, is a key process for fruit production in flowering plants. It has been shown that hormones (such as auxin and gibberellin) act in parallel with transcription factors during fruit set. Some of these are post-transcriptionally regulated by microRNAs (miRNAs). MiRNAs are a group of small non coding RNAs (21-22 nt) that act by regulating post-transcriptionally genes in plants and animals However, microRNA-regulated genetic pathways associated with tomato (Solanum lycopersicum L.) ovary development and fruit set remain poorly exploited. Here, we investigated the functional role of miRNA159/SlyGAMYBlike in tomato ovary development and fruit set. MiR159 and its targets were dynamically expressed in developing flowers, ovaries and fruit tissues. Transgenic tomato (cv. Micro-Tom) plants over-expressing the SlyMIR159 (termed OE-159) exhibited fruit set earlier when compared with control plants. Strikingly, all transgenic lines presented parthenocarpy fruits. Such developmental modification may be a result of the repression of SlyGAMYB1 in pre-anthesis ovaries, our data suggest that SlyGAMYB1 activity is important to prevent fruit set before pollination. In addition as a consequence of this repression, the miR167 node (miR167/SlyARF8 pathway) was mis-regulated in OE-159 ovaries. In addition, we observed that levels of auxin, gibberellin (GA) and abscisic acid (ABA) in pre-anthesis ovaries of several transgenic lines overexpressing the SlyMIR159 were similar to those of the control. Moreover, our experiments suggested that auxin and GA may act repressing the miR159 node during fruit set initiation, in order to release the miR167-targeted SlyARF8A expression during fruit set. Our data show how two microRNA nodes (miR159 and miR167) integrated with hormone signalling into a circuit that coordinates successive steps along ovary and fruit development. (AU)

• FAPESP's process: 13/02469-6 - Contribution of the LeGAMYB1/microRNA 159 pathway in the regulation of development of lateral organs and fruit formation in tomato (Solanum Lycopersicum) cv micro
• Grantee: Eder Marques da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate