Functional studies of selected members of the Arabidopsis formin family

Formins are multidomain proteins containing a conserved formin-homology 2 (FH2) domain, which catalyzes de novo nucleation of actin filaments. In yeast and animal cells, both mechanisms and regulation of formin function have been extensively studied, yet much less is known about action of plant formins, which considerably differ from yeast and animal ones in the domain composition. In higher plants, formins are classified into two groups, Class I and Class II, and so far, experimental data are available only for the first group members. Here I present results of experimental study of several members of the large formin family in Arabidopsis, including the characterization of a Class II formin AtFH16. Arabidopsis genome contains 21 formin-encoding genes, and though they greatly differ in their expression levels and pattern, all of them are transcriptionally active. We selected 17 homozygous T-DNA insertional mutants in 14 formin genes. Under standard cultivation conditions, no obvious phenotypic discrepancies between wild type and mutant plants were found. To impair two dominant pollen formins, an atfh3atfh5 double-mutant was prepared and even in this case, both microspore development and pollen tube growth remained unaffected. Consistently, polarized growth of tobacco pollen tubes was not altered..