Calcium - a central regulator of pollen germination and tube growth

Abstract

Pollen tubes grow rapidly by very fast rates and reach extended lengths to bring about fertilization during plant reproduction. The pollen tube grows exclusively at its tip. Fundamental for such local, tip-focused growth are the presence of internal gradients and transmembrane fluxes of ions. Consequently, vegetative pollen tube cells are an excellent single cell model system to investigate cell biological processes of vesicle transport, cytoskeleton reorganization and regulation of ion transport. The second messenger Ca(2+) has emerged as a central and crucial modulator that not only regulates but also integrates the coordination each of these processes. In this review we reflect on recent advances in our understanding of the mechanisms of Ca(2+) function in pollen tube growth, focusing on its role in basic cellular processes such as control of cell growth, vesicular transport and intracellular signaling by localized gradients of second messengers. In particular we discuss new insights into the identity and role of Ca(2+) conductive ion channels and present experimental addressable hypotheses about their regulation. This article is part of a Special Issue entitled:12th European Symposium on Calcium.

Pollen Tube Growth Regulation by Free Anions Depends on the Interaction between the Anion Channel SLAH3 and Calcium-Dependent Protein Kinases CPK2 and CPK20

“…Many of these physiological processes are interconnected, rendering the analysis of the Ca 2+ signaling cascades difficult. The current knowledge on generating Ca 2+ gradients and decoding Ca 2+ signatures in pollen tubes has recently been comprehensively reviewed (Konrad et al, 2011;Steinhorst and Kudla, 2012). Much less is known about the role of anions on pollen germination and tube growth performance (Tavares et al, 2011b).…”

A Pollen Coat–Inducible Autoinhibited Ca2+-ATPase Expressed in Stigmatic Papilla Cells Is Required for Compatible Pollination in the Brassicaceae

“…Since Brewbaker and Kwack (1963) revealed that Ca 2+ is essential for in vitro pollen tube cultures, the relationship between Ca 2+ concentration ([Ca 2+ ]) and pollen tube growth has been extensively examined (Steinhorst and Kudla, 2013). In compatible pollination using pollen grains of transgenic Arabidopsis thaliana expressing a Ca 2+ sensor protein, a cytoplasmic [Ca 2+ ] ([Ca 2+ ] cyt ) increase was observed at the potential germination site and at the tip region of the pollen tube (Iwano et al, 2004(Iwano et al, , 2009).…”

The utility of electrospun nanofibre mats for in vitro germination of Artabotrys hexapetalus pollen

“…The use of liquid or agar-gelled medium with the various ingredients is the most common physical support to germinate pollen in vitro. Earlier investigations have shown the importance of different ingredients including Ca 2+ ions 2 , boron 3 , and sucrose 4 added to media for pollen germination of different plant species in vitro. A recent study shows that a solid support matrix such as a cellulose membrane placed on top of agarose gel resulted in a high percentage of Arabidopsis pollen germination in vitro 5 .…”