Microscopic and metabolic investigations disclose the factors that lead to skin cracking in chili-type pepper fruit varieties

Abstract

The hydrophobic cuticle encasing the fruit skin surface plays critical roles during fruit development and post-harvest. Skin failure often results in the fruit surface cracking and forming a wound-periderm tissue made of suberin and lignin. The factors that make the fruit skin susceptible to cracking have yet to be fully understood. Herein, we investigated two varieties of chili peppers ( Capsicum annuum L.), Numex Garnet, whose fruit has intact skin, and Vezena Slatka, whose fruit has cracked skin. Microscopical observations, gas chromatography–mass spectrometry, biochemical and gene expression assays revealed that Vezena Slatka fruit form a thicker cuticle with greater levels of cutin monomers and hydroxycinnamic acids, and highly express key cutin-related genes. The skin of these fruit also had a lower epidermal cell density due to cells with very large perimeters, and highly express genes involved in epidermal cell differentiation. We demonstrate that skin cracking in the Vezena Slatka fruit is accompanied by a spatial accumulation of lignin-like polyphenolic compounds, without the formation of a typical wound-periderm tissues made of suberized cells. Lastly, we establish that skin cracking in chili-type pepper significantly affects fruit quality during post-harvest storage in a temperature-dependent manner. In conclusion, our data highlight cuticle thickness and epidermal cell density as two critical factors determining fruit skin susceptibility to cracking in chili-type pepper fruit.

Acknowledgements

The authors would like to thank Ilan Paran from the Department of Vegetable and Field Crops, Institute of Plant Science, Agricultural Research Organization (ARO), Volcani Center, for providing seeds of Numex Garnet and Vezena Slatka pepper fruit. We also acknowledge Amnon Lers Daniel Chalupowicz from the Department of Post-harvest Science, Institute of Post-harvest and Food Sciences, Agricultural Research Organization (ARO), Volcani Center, for their guidance during the post-harvest experiments. The authors would also like to thank Ms. Natalie Page for proofreading the manuscript.

Author contributions

O.M. executed all the experiments in this project; G.N., S.S., G.C.A. and E.M. assisted in epidermal cell counting experiments and microscopy; E.K. assisted in the cultivation of pepper and greenhouse maintenance; E.Z. assisted in electron microscopy experiments; O.M. and H.C. conceptualized and designed the project, and wrote the manuscript. All authors approved the final version of the manuscript.

Data availability

The authors declare that all the data supporting the findings of this study are available within the manuscript and its supplemental information files.

Conflict of interest

The authors declare they have no competing financial interests or personal relationships that could have influenced the work reported in this manuscript.

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