Control genetico del tamano floral en Antirrhinum majus

The main objective of this thesis is to uncover the genetic control of floral size in Antirrhinum majus. We have done a characterization of A. majus mutants. First step was the evaluation of the stability of floral size against crowding conditions and artificial foliar reduction, in wild type 165E plants. These results demonstrated that plant lateral organs tend to reduce total mass upon crowding. Leaf number proofed a stable character, while leaf size decreased. In contrary, flower number was reduced while floral size was stable. Results indicate that floral size is a stable character both under crowding and foliar reduction.The following genes of A. majus whose mutants affect floral size and proportions were selected: COMPACTS ( CO), GRANDIFLORA (GRAF) Y FORMOSA (FO). A segregation analysis in F2 populations revealed that co and fo mutants are recessive alleles while Graf mutant is a dominant allele. The mutant co shows a reduction in the size of all plant lateral organs including flowers and leaves. In the flowers we observed a size reduction of sepals, petals and carpels either due to changes in cell expansion and/or cell division, depending on the floral organ identity or the floral whorl. Graf, which almost exclusive effect flower size, shows a phenotype opposite to co with an increase in size of all floral organs. Changes are due to an increment on cell expansion in petals and cell division in sexual organs. Analysis of the double mutant, Graf co, suggests that both genes act in the same route controlling petal size. Double mutants between co and a class B floral identity gene (which also reduces floral organ size) show a synergistic effect between both genes concerning organ size and petal identity. This suggests that the two genes could participate in organ size control and petal identity in parallel routes.The mutant fo affect exclusively flowers showing bigger floral organs in the three outer whorls. Increases cell number in all floral organs. Expression level of AINTEGUMENTA is elevated in floral meristems and those of cell cycle related genes in mutant petals. Cell expansion is reduced in petals and carpels and this coincides with an up regulation of BigPetal gene. Double mutant analysis between fo and a class C flower identity gene indicates that fo effect is not specific of organ identity. The fo double mutant also shows synergism with the class C identity gene suggesting a putative participation of both genes in redundant routes in the control of petal size. The presences of pleiotropic mutants affecting all plant lateral organs, and genes that disturb only flower size indicate the presence of at least two gene groups, one controlling vegetative and reproductive growth and another flower specific one.