XVI International Botanical Congess

In male sterile33 (ms33) mutant in Arabidopsis, pollen development and stamen filament growth are both affected. Exogenous gibberellins (GAs) restored filament growth in ms33 but not pollen fertility. ms33 flowers contained low levels of GAs (GA1, GA4 and GA9) and IAA, but high level of ABA compared to the wild type. Double mutant of ms33 and spindly-1 (spy-1), a GA signal transduction mutant, showed enhanced filament growth, and produced non-viable pollen. In ms33 spy-1 growth of petals and gynoecia was also increased compared to ms33 or spy-1 flowers. These results show that spy-1 partially suppresses the effect of ms33, and that GAs have an important role in floral organ growth. Pollen development in Arabidopsis appears to require a critical balance of several hormones.