Advances in Cell Wall Dynamics and Gene Expression in Postharvest Fruit Softening

Abstract

Postharvest fruit softening is a critical determinant of fruit shelf life, significantly influencing mechanical damage susceptibility, pathogen invasion, and consumer preference. Collectively, these factors lead to substantial losses in the fruit industry. The structural modifications of cell wall and cuticle during ripening primarily govern fruit softening. The objective of this review is to synthesize recent advances and provide a comprehensive analysis of the molecular mechanisms underlying this process. In this review, we provide a comprehensive analysis of cell wall composition and softening-associated cell wall remodeling proteins. We examine recent advances in manipulating single or multiple genes encoding cell wall-modifying proteins that influence fruit softening, and identify key transcription factors regulating the expression of these gene networks. This review synthesizes current understanding of the molecular mechanisms governing fruit ripening, providing a foundation for future research in postharvest biology.

Keywords: fruit quality; polysaccharide metabolism; shelf life; transcriptional regulation; water loss.

Figure 2

(A). The model of the growing cell wall [14]. Cellulose microfibrils establish lateral connections, creating bundles and an integrated framework. Xyloglucans associate with cellulose surfaces in extended or folded conformations or are enclosed within cellulose aggregates. Pectins generate a gel-like matrix that encompasses cellulose and xyloglucan. (B). Transmission electron micrographs of TCJ (left) and ML (right) [33]. The ML between adjacent cells is rich in de-esterified homogalacturonan (HGA). PCW, primary cell wall. ML, middle lamella. TCJ, tricellular junctions. The bar (left) indicates 5 μm, and the bar (right) indicates 1 μm. (C). Schematic diagrams of molecular structures of several dominant cell wall polysaccharides [14]. (i) Xyloglucans. (ii) Homogalacturonan. (iii) Rhamnogalacturonan-I.

Figure 1

Shifts in respiratory rate and ethylene production in climacteric or non-climacteric fruit during development, maturation, and senescence [9]. Solid lines represent climacteric fruits (e.g., apples, bananas, and kiwifruits), and dashed lines correspond to non-climacteric fruits (e.g., grapes, strawberries, and cherries).

Figure 3

A model for the cell wall remodeling protein-mediated regulatory network of fruit softening. Arrows and T bars indicate promoting and inhibitory effects, respectively. Blue and pink colors represent positive and negative regulators of fruit softening, respectively.