CmbZIP11 regulates CmPMT1/15 affecting homogalacturonan methyl-esterification and fruit softening in melon

Abstract

Homogalacturonan (HG) methyl-esterified modification pathway genome-wide expression analysis in two texture types of oriental melon fruits ‘HDB’ (crisp) and ‘HPM’ (mealy) at different developmental stages revealed that the Golgi S-adenosyl-L-methionine transporter gene CmGoSAMT1 and the pectin methyltransferase genes CmPMT1 and CmPMT15 were critical functional genes for HG methyl-esterification in melon. However, overexpression of CmGoSAMT1 cannot significantly alter fruit hardness, whereas overexpression of CmPMT1 and CmPMT15 appears to cause the fruit to synthesize more highly methyl-esterified HG, which are separated from each other due to the ‘steric effect’ of methyl groups on the C-6 carboxyl of D-GalA, and cannot be cross-linked by Ca²⁺ to form an ‘egg-box’ matrix making it more accessible to de-methylating and degrading enzymes (CmPMEs, CmPGs, and CmPLs), thus fruit susceptible to softening. In addition, a transcription factor CmbZIP11 co-expressed with CmPMT1 and CmPMT15 was verified, which could activate the expression of CmPMT1 and CmPMT15 to regulate the methyl-esterification of HG, thereby affecting fruit softening.

Acknowledgements

This work was sponsored by China Agriculture Research System of MOF and MARA (CARS-25) and Liao Ning Revitalization Talents Program (XLYC2402014). We appreciate Assoc. Prof. Tao Liu and Assoc. Prof. Jian Pan from College of Horticulture, Shenyang Agricultural University (SYAU), for their suggestions regarding the adjustment of the article. We also thank Lecturer Weisheng Niu from College of Engineering, SYAU, for his help with using the FT-IR spectrometer. We would also like to thank Dr. Fei Luo and Dr. Shuting Zhang from College of Horticulture, SYAU in Y1H experiment.

Authors contributions

H.P. designed and performed the experiments, analyzed the data, and wrote the manuscript. Y.S. conducted the identification of CmPGs family. R.W. conducted the identification of CmPLs family. H.Q. supervised the project. All authors have read and approved the final version of the manuscript.

Data availability

All data in this study are included in the published article and its supplementary information.

Conflicts of interest statement

The authors declare that they have no competing interests.

Supplementary material

Supplementary material is available at Horticulture Research online.

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