title: Addition of Phenylboronic Acid to Malus domestica Pollen Tubes Alters Calcium Dynamics, Disrupts Actin Filaments and Affects Cell Wall Architecture.
abstract: A key role of boron in plants is to cross-link the cell wall pectic polysaccharide rhamnogalacturonan-II (RG-II) through borate diester linkages. Phenylboronic acid (PBA) can form the same reversible ester bonds but cannot cross-link two molecules, so can be used as an antagonist to study the function of boron. This study aimed to evaluate the effect of PBA on apple (Malus domestica) pollen tube growth and the underlying regulatory mechanism. We observed that PBA caused an inhibition of pollen germination, tube growth and led to pollen tube morphological abnormalities. Fluorescent labeling, coupled with a scanning ion-selective electrode technique, revealed that PBA induced an increase in extracellular Ca2+ influx, thereby elevating the cytosolic Ca2+ concentration [Ca2+]c and disrupting the [Ca2+]c gradient, which is critical for pollen tube growth. Moreover the organization of actin filaments was severely perturbed by the PBA treatment. Immunolocalization studies and fluorescent labeling, together with Fourier-transform infrared analysis (FTIR) suggested that PBA caused an increase in the abundance of callose, de-esterified pectins and arabinogalactan proteins (AGPs) at the tip. However, it had no effect on the deposition of the wall polymers cellulose. These effects are similar to those of boron deficiency in roots and other organs, indicating that PBA can induce boron deficiency symptoms. The results provide new insights into the roles of boron in pollen tube development, which likely include regulating [Ca2+]c and the formation of the actin cytoskeleton, in addition to the synthesis and assembly of cell wall components.
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors.forename: Kefeng
authors.initials: K
authors.lastname: Fang
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors.forename: Sai
authors.initials: S
authors.lastname: Gao
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Xing
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors.forename: Qingqin
authors.initials: Q
authors.lastname: Cao
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture, Beijing 102206, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D001881:Borates / Q000494:pharmacology; D001897:Boronic Acids / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D017610:Calcium Compounds / Q000494:pharmacology; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D004951:Esterification; D018525:Germination / Q000187:drug effects; D027845:Malus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D009088:Mucoproteins / Q000378:metabolism; D010368:Pectins / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D053205:Pollen Tube / Q000033:anatomy & histology / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001881:Borates; D001897:Boronic Acids; D017610:Calcium Compounds; D009088:Mucoproteins; D010940:Plant Proteins; C006619:arabinogalactan proteins; C031316:calcium borate; D010368:Pectins; D002482:Cellulose; C010686:benzeneboronic acid; D002118:Calcium