期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：33
DOI：10.1073/pnas.2102486118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
A tomato fruit ripening–specific transcription factor,
SlLOB1 predominantly influences fruit cell wall–related gene regulation and textural changes during fruit maturation and thus is distinct from broadly acting ripening transcription factors described to date that influence many ripening processes. As such,
SlLOB1 is an intermediate regulator primarily influencing a physiological subdomain of the overall ripening transition.
Fruit softening is a key component of the irreversible ripening program, contributing to the 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 late maturation and ripening of locule and pericarp tissues.
SlLOB1 repression in transgenic fruit impedes softening, while overexpression throughout the plant under the direction of the 35s promoter 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
Sl
LOB1 RNA interference lines, while
EXP1 is induced in
Sl
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,
Sl
LOB1 participates in a regulatory subcircuit predominant to cell wall dynamics and softening.
