背景回顾：Fruit softening is a key component of the irreversible ripening program, contributing to the palatability necessary for frugivore-mediated seed dispersal. 

提出问题：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.

主要发现：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.

结果1-基因功能：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. 

结果2-下游机制：Transcript and protein levels of the wall-loosening protein EXPANSIN1 (EXP1) are strongly suppressed in SlLOB1 RNA interference lines, while EXP1 is induced in SlLOB1-overexpressing transgenic leaves and fruit. 

结论：In contrast to the role of ethylene and previously characterized ripening TFs, which are comprehensive facilitators of ripening phenomena including softening, SlLOB1 participates in a regulatory subcircuit predominant to cell wall dynamics and softening.

 摘 要 

果实变软是果实成熟过程中不可逆进程中的关键组成部分，有助于增加果实的可食性，促进由食果动物介导种子散播。该过程潜在的果实质感变化十分复杂，主要是由细胞壁重塑以及细胞粘附和膨压变化所引起。目前已经鉴定了很多调控果实成熟相关转录因子，这些基因影响大多数典型的成熟相关的生理过程。本文中，作者鉴定了一个番茄果实成熟特异性转录因子SlLOB1基因，该基因会在番茄果实的子房和果皮组织的成熟后期，上调很多与细胞壁相关基因。抑制番茄中SlLOB1基因的表达会导致果实不容易变软，而通过35S启动子来过表达SlLOB1基因则会导致细胞壁相关基因的提前表达，果实过早软化。细胞壁松弛蛋白EXPANSIN1的转录和蛋白水平在SlLOB1 RNA干扰株系中被抑制，而在SlLOB1过表达株系的叶片和果实中被诱导。乙烯以及先前鉴定的成熟相关转录因子大多能够整体促进果实成熟，其中包括果实软化，而SlLOB1基因特定的参与果实细胞壁动态和软化的调控亚支路。