title: Boron Toxicity Causes Multiple Effects on Malus domestica Pollen Tube Growth.
abstract: Boron is an important micronutrient for plants. However, boron is also toxic to cells at high concentrations, although the mechanism of this toxicity is not known. This study aimed to evaluate the effect of boron toxicity on Malus domestica pollen tube growth and its possible regulatory pathway. Our results showed that a high concentration of boron inhibited pollen germination and tube growth and led to the morphological abnormality of pollen tubes. Fluorescent labeling coupled with a scanning ion-selective electrode technique detected that boron toxicity could decrease [Ca(2+)]c and induce the disappearance of the [Ca(2+)]c gradient, which are critical for pollen tube polar growth. Actin filaments were therefore altered by boron toxicity. Immuno-localization and fluorescence labeling, together with fourier-transform infrared analysis, suggested that boron toxicity influenced the accumulation and distribution of callose, de-esterified pectins, esterified pectins, and arabinogalactan proteins in pollen tubes. All of the above results provide new insights into the regulatory role of boron in pollen tube development. In summary, boron likely plays a structural and regulatory role in relation to [Ca(2+)]c, actin cytoskeleton and cell wall components and thus regulates Malus domestica pollen germination and tube polar growth.
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture Beijing, 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, 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, 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, China.
authors.forename: Qing
authors.initials: Q
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, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Yang
authors.affiliation: Beijing Key Laboratory for Agricultural Application and New Technique, College of Plant Science and Technology, Beijing University of Agriculture Beijing, 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, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
keywords: Malus domestica; actin; arabinogalactan proteins; boron toxicity; calcium; callose; pectin