Microinjection of guanine nucleotide analogues into lily pollen tubes results in isodiametric tip expansion

Heterotrimeric and small G-proteins are supposed to participate in tip growth of plant cells. Quantitative changes in tip growth rate after introduction of non-hydrolysable guanine nucleotide analogues (NA) into lily pollen tubes have been interpreted as support for the hypothesis that heterotrimeric G-proteins regulate tube elongation (Ma et al., 1999([11])). Here, we report that microinjection of guanine NA into lily pollen tubes causes loss of growth polarity, resulting in isodiametric tip swelling. Our results are compatible with current models suggesting an involvement of plant Rho-related small G-proteins (Rop) in the maintenance of pollen tube polarity and in tip morphogenesis.