Moya-León Maria Alejandra, Mattus-Araya Elena, Herrera Raul
Instituto de Ciencias Biológicas, Universidad de Talca, Talca, Chile.
Front Plant Sci. 2019 May 15;10:615. doi: 10.3389/fpls.2019.00615. eCollection 2019.
Changes in fruit texture taking place during ripening, described as softening, are mainly due to alterations in structure and/or composition of the cell wall. Several non-covalent interactions between the three carbohydrate polymers of the cell wall, cellulose, pectins and hemicellulose, and many structural proteins and ions, enable a complex structure. During softening, the disassembly of the cell wall structure takes place, mediated by a complete set of cell wall degrading enzymes or proteins. Softening is a coordinated event that requires the orchestrated participation of a wide variety of proteins. Plant hormones and a set of transcription factors are the organizers of this multi-protein effort. Strawberry is a non climacteric fruit that softens intensively during the last stages of development. The Chilean strawberry fruit (), the maternal relative of the commercial strawberry ( × ), softens even faster than commercial strawberry. Softening of the Chilean strawberry fruit has been studied at different levels: changes in cell wall polymers, activity of cell wall degrading enzymes and transcriptional changes of their genes, providing a general view of the complex process. The search for the 'orchestra director' that could coordinate softening events in strawberry fruit has been focussed on hormones like ABA and auxins, and more precisely the relation ABA/AUX. These hormones regulate the expression of many cell wall degrading enzyme genes, and this massive transcriptional change that takes place involves the participation of key transcriptional factors (TF). This review provides an update of the present knowledge regarding the softening of strawberry fruit. Nevertheless, the entire softening process is still under active research especially for the great influence of texture on fruit quality and its high impact on fruit shelf life, and therefore it is expected that new and promising information will illuminate the field in the near future.
果实成熟过程中发生的质地变化，即软化，主要是由于细胞壁结构和/或组成的改变。细胞壁的三种碳水化合物聚合物（纤维素、果胶和半纤维素）与许多结构蛋白和离子之间的几种非共价相互作用，形成了一个复杂的结构。在软化过程中，细胞壁结构的拆解是由一整套细胞壁降解酶或蛋白质介导的。软化是一个协调的过程，需要多种蛋白质的精心参与。植物激素和一组转录因子是这种多蛋白作用的组织者。草莓是一种非跃变型果实，在发育的最后阶段会剧烈软化。智利草莓果实（）是商业草莓（×）的母本亲缘种，其软化速度比商业草莓还要快。已经从不同层面研究了智利草莓果实的软化：细胞壁聚合物的变化、细胞壁降解酶的活性及其基因的转录变化，从而对这一复杂过程有了一个总体认识。寻找能够协调草莓果实软化事件的“指挥者”的研究主要集中在脱落酸（ABA）和生长素等激素上，更确切地说是ABA/生长素的关系。这些激素调节许多细胞壁降解酶基因的表达，而这种发生的大规模转录变化涉及关键转录因子（TF）的参与。本综述提供了关于草莓果实软化的现有知识的最新情况。然而，整个软化过程仍在积极研究中，特别是因为质地对果实品质有很大影响，对果实货架期有很高影响，因此预计在不久的将来会有新的、有前景的信息照亮这个领域。
