Fruit softening is a key component of the irreversible ripening program, contributing to palatability necessary for frugivore-mediated seed dispersal. The underlying textural changes are complex, and result from cell wall remodeling and changes in both cell adhesion and turgor. While a number of transcription factors (TFs) that regulate ripening have been identified, these affect most canonical ripening-related physiological processes. Here we show that a tomato fruit ripening-specific LATERAL ORGAN BOUNDRIES (LOB) TF, SlLOB1, up-regulates a suite of cell wall associated genes during ripening. SlLOB1 repression in transgenic fruit impedes softening, while over-expression confers precocious induction of cell wall gene expression and premature softening. Transcript and protein levels of the wall loosening protein EXPANSIN1 (EXP1) are strongly suppressed in LOB1 RNAi lines, while EXP1 is induced in LOB1-overexpressing transgenic leaves and fruit. In contrast to the role of ethylene and previously characterized ripening TFs, which are comprehensive facilitators of ripening phenomena, including softening, LOB1 participates in a regulatory sub-circuit specific to cell wall dynamics and softening.

Tomato lateral organ boundaries transcription factor, SlLOB1 specifically regulates the cell wall and softening component of ripening

ACS Fall 2020 Virtual Meeting

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