Pump up the volume - a central role for the plasma membrane H+ pump in pollen germination and tube growth

Abstract

The plasma membrane H(+) ATPase is a member of the P-ATPase family transporting H(+) from the cytosol to the extracellular space and thus energizing the plasma membrane for the uptake of ions and nutrients. As a housekeeping gene, this protein can be detected in almost every plant cell including the exclusive expression of specific isoforms in pollen grains and tubes where its activity is a prerequisite for successful germination and growth of pollen tubes. This review summarizes the current knowledge on pollen PM H(+) ATPases and hypothesizes a central role for pollen-specific isoforms of this protein in tube growth. External as well as cytosolic signals from signal transduction and metabolic pathways are integrated by the PM H(+) ATPase and directly translated to tube growth rates, allocating the PM H(+) ATPase to an essential node in the signalling network of pollen tubes in their race to the ovule.

Regulation of Petunia Pollen Tube Growth by Phytohormones: Identification of Their Potential Targets

“…This conclusion is supported by the orthovanadate-sensitive hyperpolarization of pollen PM observed in the presence of IAA, ABA and GA 3 . In accordance with recent data on important role of this enzyme in pollen tube polar growth [7], it is not surprising that the growth-stimulating action of the hormones most likely involves their impact on the proton pump. One more hormonal effect related to their action on pollen PM H + -ATPase is expressed in the change of its lateral membrane allocation in pollen tube PM.…”

“…A fine-tuned network of cellular processes is required to regulate the germination of pollen grains and the elongation of pollen tubes. These processes include a dynamic organization of the cytoskeleton, vesicle and protein trafficking, establishing intracellular tip-localized Ca 2+ and pH gradients, an active metabolism and signal transduction pathways [1][2][3][4][5][6][7][8]. At present, understanding the operation of the highly coordinated regulatory pathways that control  Corresponding author: Lidia Kovaleva, professor, research field: pollination and fertilization in plants (hormonal signaling).…”

“…Addressing this problem, the two important circumstances were taken into account. First, the plasma membrane (PM) H + -ATPase is known to energize the pollen PM for nutrient, ion and water uptake, and additionally its activity directly affects both the germination and growth of pollen tubes [7]. In addition, this enzyme may serve as a signaling target in osmosensing and osmoregulation of pollen tubes [15] and generally is capable of behaving as an essential node in their signaling network.…”

Signaling with Ions: The Keystone for Apical Cell Growth and Morphogenesis in Pollen Tubes

“…PM voltage has been determined to be around 2130 mV when measured on the shank of PTs (Mouline et al, 2002;Griessner and Obermeyer, 2003;Becker et al, 2004), a resting potential slightly more negative than the K + equilibrium (Mouline et al, 2002). This hyperpolarization is likely driven by H + -ATPase activity (Lang et al, 2014). Unfortunately, the apical voltage remains unknown, since it is not possible to impale an electrode at the tip without provoking tube burst.…”

Sniff and run—the chemistry of attraction

“…Then, in extremely short time, not only metabolic activity has to be boosted rapidly to sustain rapid growth of the pollen tube, but also the polarity of the emerging cell has to be adjusted efficiently in concert with chemoattractive signals from the egg cell and the conductive tissue of the style. In their review, Lang et al (2014) focus on the role of proton pumps as synchronisers of the signalling. The polar growth of the pollen tube relies on an oscillatory network of calcium-dependent signalling, actin dynamics, and vesicle transport to the growing tip that is guided and modulated by chemical signals from the female partner (reviewed in Vidali and Hepler 2001).…”