CONICET | Buscador de Institutos y Recursos Humanos

After pollen grains germinate on the stigma, pollen tubes elongate within the pistil to transport sperms to female gametophytes for fertilization. During pollination, pollen tubes perceive style signals triggering cytoplasmic events required for tip growth. We characterized two pollen-specific receptor-like kinases, LePRK1 and LePRK2, from tomato pollen involved in transducing style signals. We showed over-expression of LePRK2-eGFP significantly decreased pollen tube length and increased tube tip width, relative to eGFP tubes. Site-directed mutagenesis in two putative phosphorylation motifs in the cytoplasmic juxtamembrane (JM) domain and overexpression in tobacco pollen showed that both motifs have opposite effects in regulating pollen tube length. We also used pollen tubes as a single cell system to study the mechanistic of polarized and oscillatory growth. Tomato pollen tubes showed a non-continuous growth rate and Ca2+ oscillated with the same period but out of phase. We also study the participation of aquaporins mediating water and solutes transport during pollen tube elongation. We found AtTIP5;1 and AtTIP1;3 are the only aquaporins selectively and highly expressed in Arabidopsis thaliana pollen. They both showed urea and water transport. We found that in tip1;3 and tip5;1 homozygous double mutant plants, pollen tube length was significantly reduced under nitrogen starvation.