The tender pod is the primary edible part of the snap bean ( Phaseolus vulgaris L.), and the level of suture fiber content is one of the key factors affecting its edible quality. To elucidate the key regulatory mechanisms and metabolic basis underlying suture fiber formation in pods, this study employed the high-suture-fiber-content bean cultivar ‘P1171’ and the low-suture-fiber-content cultivar ‘P16192’. We conducted cytological observations, fiber content measurements, transcriptomic, and metabolomic analyses. Results indicate that increased pod suture fiber content in snap beans results from phloem fiber proliferation, and that crude fiber content is significantly correlated with cellulose content within the fiber fraction. Transcriptome and metabolome analyses indicated that starch and sucrose metabolism pathways, as well as secondary metabolite biosynthesis pathways, are closely linked to cellulose synthesis. These pathway-associated metabolites, including UDP-glucose, ethylene(ETH), jasmonic acid(JA), and flavonoids, showed significant correlations with the differentially expressed genes Phvul.005G082800, Phvul.003G268600, Phvul.006G031700, Phvul.008G213800, Phvul.011G189200, Phvul.011G189300, Phvul.002G043100, Phvul.002G042900, and Phvul.001G083000. We therefore hypothesize that variations in the expression levels of these genes across different cultivars may lead to changes in related metabolites, ultimately resulting in differences in fiber synthesis. This study systematically investigated the molecular mechanisms underlying fiber synthesis in the suture tissue of snap beans through integrated transcriptomic and metabolomic analyses. This work lays a foundation for further exploration of the regulatory networks governing cellulose-related synthesis genes in plant fiber formation, offering potential avenues to improve crop quality, enhance snap bean traits, and advance breeding programs. • Confirm cellulose as the primary cause of increased fiber in bean pod sutures. • Directly observe fibrous deposition occurring specifically in the phloem cell layer. • Decipher how key genes and metabolites trigger fiber cell thickening via a specific pathway. • Link the key molecular expression directly to reduced pod edible quality.
Mu et al. (Sun,) studied this question.