A Chimeric TGA Repressor Slows Down Fruit Maturation and Ripening in Tomato Article - 2022

Martine Lemaire-Chamley, Claude Koutouan, Joana Jorly, Julien Assali, Takuya Yoshida, Marilise Nogueira, Takayuki Tohge, Carine Ferrand, Lázaro Peres, Erika Asamizu, Hiroshi Ezura, Paul Fraser, Mohammad-Reza Hajirezaei, Alisdair Fernie, Christophe Rothan

Martine Lemaire-Chamley, Claude Koutouan, Joana Jorly, Julien Assali, Takuya Yoshida, Marilise Nogueira, Takayuki Tohge, Carine Ferrand, Lázaro Peres, Erika Asamizu, Hiroshi Ezura, Paul Fraser, Mohammad-Reza Hajirezaei, Alisdair Fernie, Christophe Rothan, « A Chimeric TGA Repressor Slows Down Fruit Maturation and Ripening in Tomato  », Plant and Cell Physiology, 2022, pp. 120–134. ISSN 0032-0781

Abstract

Abstract The bZIP transcription factor (TF) SlTGA2.2 was previously highlighted as a possible hub in a network regulating fruit growth and transition to ripening (maturation phase). It belongs to a clade of transcription factors well known for their involvement in the regulation of the salicylic acid (SA) – dependent systemic acquired resistance (SAR). To investigate if this TGA TF plays a role in tomato fruit growth and maturation, we took advantage of the fruit-specific SlPPC2 promoter (PPC2pro) to target the expression of a SlTGA2.2-SRDX chimeric repressor in a developmental window restricted to early fruit growth and maturation. Here, we show that this SlTGA2.2-SRDX repressor alters early fruit development and metabolism, including chloroplast number and structure, considerably extends the time necessary to reach the mature green stage and slows down fruit ripening. RNAseq and plant hormone analyses reveal that PPC2pro:SlTGA2.2-SRDX fruits are maintained in an immature stage as long as PPC2pro is active, through early modifications of plant hormonal signalling and down-regulation of MADS-RIN and NAC-NOR ripening regulators. Once PPC2pro becomes inactive and therefore SlTGA2.2-SRDX expression is reduced, ripening can proceed, albeit at a slower pace than normal. Altogether, this work emphasizes the developmental continuum between fruit growth, maturation and ripening and provides a useful tool to alter and study the molecular bases of tomato fruit transition to ripening.

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