The effects of PROTEOLYSIS6 (PRT6) gene suppression on the expression patterns of tomato ethylene response factors

Abstract

The ubiquitin-mediated proteolysis via Arg N-degron branch regulates various plant developmental processes and responds to multiple stresses. Nevertheless, limited information is available on the significance of the pathway during fruit ripening. This study reports that the suppression of PROTEOLYSIS6 (PRT6) E3 ligase in tomato through RNAi altered the gene expression of four Ethylene Response Factors (ERFs) (SIERF77, SIERF2, JERF1, and JERF3). The transient expression of 35S::PRT6_RNAi and PG::PRT6_RNAi constructs successfully down-regulated the PRT6 expression in leaves and mature green fruits through 35S promoter, and in breaker-stage fruits via polygalacturonase (PG) promoter, respectively. Reverse transcription-quantitative PCR (RT-qPCR) analysis showed an increased expression of SIERF77, SIERF2, and JERF1 but decreased JERF3 expression in the leaves and mature green fruits agroinfiltrated with 35S::PRT6_RNAi. Ripening-specific SIERF2 showed an increased expression in the breaker-stage fruits agroinfiltrated with PG::PRT6_RNAi, supporting the hypothesis that a low expression level of PRT6 affected the expression patterns of ERFs in specific tissues of tomato. Conversely, the expression of pectin methylesterase (PME) decreased in the breaker fruits. The four orthologues of tomato ERFs had been found to be the Arg N-degron substrates in Arabidopsis, with physiological functions being regulated at the protein level. This study showed that the suppression of PRT6 influenced the expression of these four transcription factors and PME.