RESUMO
Phosphatidylinositol 3-kinase has been reported to be important for normal plant growth. To characterize the role of the enzyme further, we attempted to isolate Arabidopsis (Arabidopsis thaliana) plants that do not express the gene, but we could not recover homozygous mutant plants. The progeny of VPS34/vps34 heterozygous plants, harboring a T-DNA insertion, showed a segregation ratio of 1:1:0 for wild-type, heterozygous, and homozygous mutant plants, indicating a gametophytic defect. Genetic transmission analysis showed that the abnormal segregation ratio was due to failure to transmit the mutant allele through the male gametophyte. Microscopic observation revealed that 2-fold higher proportions of pollen grains in heterozygous plants than wild-type plants were dead or showed reduced numbers of nuclei. Many mature pollen grains from the heterozygous plants contained large vacuoles even until the mature pollen stage, whereas pollen from wild-type plants contained many small vacuoles beginning from the vacuolated pollen stage, which indicated that vacuoles in many of the heterozygous mutant pollen did not undergo normal fission after the first mitotic division. Taken together, our results suggest that phosphatidylinositol 3-kinase is essential for vacuole reorganization and nuclear division during pollen development.
Assuntos
Proteínas de Arabidopsis/fisiologia , Arabidopsis/enzimologia , Fosfatidilinositol 3-Quinases/fisiologia , Pólen/enzimologia , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Divisão do Núcleo Celular/genética , Segregação de Cromossomos/genética , Cruzamentos Genéticos , Germinação , Microscopia Eletrônica de Transmissão , Mutagênese Insercional , Fenótipo , Fosfatidilinositol 3-Quinases/genética , Pólen/crescimento & desenvolvimento , Pólen/ultraestrutura , Sementes/enzimologia , Sementes/genética , Sementes/crescimento & desenvolvimento , Vacúolos/enzimologia , Vacúolos/ultraestruturaRESUMO
The T-DNA gene-trap system has been efficiently used to elucidate gene functions in plants. We report here a functional analysis of a cysteine protease gene, OsCP1, isolated from a pool of T-DNA insertional rice. GUS assay with the T-DNA tagged line indicated that the OsCP1 promoter was highly active in the rice anther. Sequence analysis revealed that the deduced amino acid sequence of OsCP1 was homologous to those of papain family cysteine proteases containing the highly conserved interspersed amino acid motif, ERFNIN. This result suggested that the gene encodes a cysteine protease in rice. We also identified a suppressed mutant from T2 progeny of the T-DNA tagged line. The mutant showed a significant defect in pollen development. Taken together, the results demonstrated that OsCP1 is a cysteine protease gene that might play an important role in pollen development.