iProXProteomicsPeisheng MaoMedicago Sativahttp://www.iprox.org/page/project.html?id=IPX0015949000maops@cau.edu.cnChina Agriculture University College of Grassland Science and TechnologyiProXfalsealfalfa pollen tube elongation in response to boron deficiency based on proteomicsBoron is an essential micronutrient for plant reproductive growth, and its key function in plants is mediated through cross-linking with the cell wall pectic polysaccharide rhamnogalacturonan II. As an important forage crop, boron deficiency in alfalfa inhibits pollen tube elongation, leading to floret abortion and reduced seed set. However, the molecular mechanism by which boron deficiency regulates pectin to affect alfalfa pollen-tube elongation remains unclear. In this study, we demonstrated that under boron-deficient conditions, methyl-esterified pectin shifts from an apical localization to subapical and shank regions, whereas deesterified pectin becames predominantly concentrated at the apex of pollen tubes. Proteomic analysis of pollen tubes subjected to different boron concentrations revealed significant enrichment of pectin methylesterase activity, polygalacturonase activity, and carbohydrate metabolic processes. Volcano plot analysis of the 56 shared differentially expressed proteins identified two pectin methylesterase inhibitors (MsPMEI14 and MsPMEI15). Chromosomal localization, phylogenetic, and cis-element analyses indicated that MsPMEI14 and MsPMEI15 were evolutionarily conserved. Subcellular localization showed that both MsPMEI14 and MsPMEI15 were localized in the cytoplasm, while MsPMEI14 was also localized in the nucleus, suggesting that MsPMEI14 might be the main factor responsible for the altered spatial distribution of pectin between the pollen tube apex and shank under low-boron conditions, phenotypic analysis demonstrated that mutation of PMEI suppresses pollen tube elongation under low-boron conditions.Wed Mar 04 00:00:00 GMT 2026PXD0751803879