MOLECULAR MECHANISMS OF POLLEN-PISTIL INTERACTIONS IN TOMATO AND ARABIDOPSIS PLANTS

MUSCHIETTI J; WENGIER D; SOTO G; SALEM T; BARBERINI L; MAZZELLA A

Tucuman

Congreso; SAIB; 2009

After pollen grains germinate on the stigma, pollen tubes elongatewithin the pistil to transport sperms to female gametophytes forfertilization. During pollination, pollen tubes perceive style signalstriggering cytoplasmic events required for tip growth.We characterized two pollen-specific receptor-like kinases,LePRK1 and LePRK2, from tomato pollen involved in transducingstyle signals. We showed over-expression of LePRK2-eGFPsignificantly decreased pollen tube length and increased tube tipwidth, relative to eGFP tubes. Site-directed mutagenesis in twoputative phosphorylation motifs in the cytoplasmic juxtamembrane(JM) domain and overexpression in tobacco pollen showed thatboth motifs have opposite effects in regulating pollen tube length.We also used pollen tubes as a single cell system to study themechanistic of polarized and oscillatory growth. Tomato pollentubes showed a non-continuous growth rate and Ca2+ oscillated withthe same period but out of phase.We also study the participation of aquaporins mediating water andsolutes transport during pollen tube elongation. We found AtTIP5;1and AtTIP1;3 are the only aquaporins selectively and highlyexpressed in Arabidopsis thaliana pollen. They both showed ureaand water transport. We found that in tip1;3 and tip5;1 homozygousdouble mutant plants, pollen tube length was significantly reducedunder nitrogen starvation.