Regulation of pollen tube growth by cellular pH and ions

Rice myo‐inositol‐3‐phosphate synthase 2 (RINO2) alleviates heat injury‐induced impairment in pollen germination and tube growth by modulating Ca2+ signaling and actin filament cytoskeleton

“…The fluctuation of tip-focused Ca 2+ gradient and Ca 2+ concentration in the pollen tube could be sensitively utilized to regulate the apical growth and actin filament polymerization of pollen tubes (Ruelland et al, 2015). Previous studies had proved that Ca 2+ participated in the regulation of PG and PTG at the downstream of PIs (Wang et al, 2015;Zhou et al, 2022), in which PI (4,5) P 2 might modulate the stability of actin filaments and pollen tube growth in concert with oscillatory Ca 2+ gradients (Cheung & Wu, 2008). IP3 could modulate the tip-focused Ca 2+ gradient by activating the release of Ca 2+ from internal stores (Vidali et al, 2001).…”

Transcriptomic Insight into the Pollen Tube Growth of Olea europaea L. subsp. europaea Reveals Reprogramming and Pollen-Specific Genes Including New Transcription Factors

“…Ca was known to be a key messenger for PT growth [ 1 ] sensitive to inositol signalling [ 10 ], and both processes appeared during PT growth. Olive PT Ca transport was up-regulated (KM-3 cluster in Figure 4 ) while phosphatidyl inositol biosynthesis is significantly down-regulated in the 0→1 h transition (0→1 h DOWN panel in Figure 2 and the corresponding KEGG pathways in Appendix A.9 ).…”

“…This may explain the presence of a putative aquaporin TIP2-1 (Oleur061Scf0430g00024.1, DELTA-TIP) among the ubiquitous genes that can be regulated by cyclin-B1-2 (Oleur061Scf3133g07005.1) which is also a ubiquitous gene. Ion balance would be required in olive pollen to maintain polarity through microfilament skeleton, signalling, and oxidative status of male gametes, as described in other species [ 10 , 75 ], as well as to preserve the cylindrical shape and osmolarity of growing PT [ 84 , 85 , 86 ], because ions and water are used to fill the new volume and sustain turgor pressure [ 15 ].…”

“…The PT grows very rapidly through the style towards the ovules in an energy-demanding process where apoplasmic sucrose accumulated in mature pollen is consumed without any need for sucrose uptake [ 6 ]. Only the PT tip enlarges [ 7 ], depending on cytoskeleton reorganisation for organelle and vesicle trafficking [ 8 ] in a profilin-modulated assembly of actin microfilaments [ 9 ] with cell wall biosynthesis at the tip, generation of ROS and nitric oxide, pH homeostasis, energy metabolism, protein folding and degradation (reviewed in [ 1 ]), Ca gradient and other ion fluxes, together with aquaporins-dependent water transport, to avoid osmotic stress in coordination with ion transporters in the trans-Golgi network and plasma membrane proton pumps [ 10 ]. An increase in autophagy due to the high metabolic demand of PT growth was recently reported [ 11 ].…”