SIZE MATTERS IN FLORAL DEVELOPMENT

LUCIANA, DELGADO-BENARROCH; MARIA, MANCHADO ROJO; PERLA, GOMEZ-DI MARCO; JULIA, WEISS; MARCOS, EGEA-CORTINES

AMSTERDAM

Congreso; IX WORLD PETUNIA DAYS; 2007

The final size of organs is the consequence of the interaction between a genetic program controlling organ development and environmental cues that are interpreted by the underlying morphogenetic process (Weiss et aL, 2005). We have studied mutations that affect floral size in Antirrhinum and found several types     of mutations with clear-cut functions. All the mutants found affect floral size by changes in cell division and/or cell expansion. In most cases, changes in these two basic processes seem to be organ specific suggesting an underlying interaction between organ identity and growth. Thus the recessive formosa gene acts as a repressor of floral size, mainly via cell division but is epistatic over plena in terms of floral size, changing its effect to cell expansion in this genetic background. Two genes compacta and Grandiflora control petal size via cell expansion. The mutant Graf is epistatic over co suggesting their action in a single pathway. Double mutant combinations of co with the weak B function allele deficiens nicotianoides show a synergistic interaction in petal identity, uncovering a hidden effect of co on B function establishment and/or maintenance. But floral size is an important parameter for pollination, an event driving fitness in strict allogamous like Antirrhinum.sp. Total floral display i.e. floral number is highly influenced by leaf area but floral size is not affected, suggesting that floral size development is environmentally canalized (Bayo-Canha, et al.,2007). Furthermore, floral size seems to be canalized in terms of environmental cues that affect overall growth like intraspecific competition. This canalization is probably important for pollination success and seems to be dependent on the proper establishment of a floral specific cell expansion program. Under intraspecific competitive conditions, floral size in Graf mutants becomes extremely variable, and sometimes collapses altogether (Delgado-Benarroch, et a/., 2007).