RESUMO
MAIN CONCLUSION: In Brachiaria brizantha BbrizSERK1, BbrizSERK2 and BbrizSERK3 were identified. SERK expression marks somatic embryogenesis, sexual MMC, and sexual and apomictic PMC. BbrizSERK3 might have a regulatory role in reproductive development. Somatic embryogenesis receptor-like kinase (SERK) consists of plasma membrane receptor genes that have been characterized in various species, associated with several aspects of plant development, including reproduction. SERK genes are involved in anther development and in early embryo development in sexual and asexual seed formation. To comprehend the complexity of the SERK genes and their function in Brachiaria reproduction, we performed a homology-based search in a genomic database of a sexual B. brizantha and identified sequences of three SERK genes, BbrizSERK1, BbrizSERK2, and BbrizSERK3. RNASeq data showed equivalent abundance of BbrizSERK1 and BbrizSERK2 transcripts in ovaries at early megasporogenesis of sexuals and apomicts, while BbrizSERK3 transcripts were more abundant in ovaries of sexuals than in apomicts. BbrizSERK3 results in three coding sequences due to alternative splicing, among them Variant 1 results in a protein with all the predicted domains of a SERK. BbrizSERK transcripts were detected in male reproductive tissues of both sexual and apomictic plants, suggesting a role in controlling anther development. BbrizSERK transcripts were detected early in ovule development, in the integuments, and in the megaspore mother cell of the sexual plant, but not in the cells that give rise to apomictic embryo sacs, suggesting a role in female reproductive development of sexuals. This paper provides evidences that SERK genes plays a role in the onset and establishment of somatic embryogenesis and in the reproductive development of B. brizantha and suggests a distinct role of BbrizSERK in apomixis initiation.
Assuntos
Brachiaria/crescimento & desenvolvimento , Brachiaria/genética , Regulação da Expressão Gênica de Plantas , Desenvolvimento Vegetal/genética , Reprodução/genética , Sementes/crescimento & desenvolvimento , Sementes/genética , Regulação da Expressão Gênica no Desenvolvimento , Genes de Plantas , Técnicas de Embriogênese Somática de PlantasRESUMO
Brachiaria brizantha is a forage grass of the Poaceae family. Introduced from Africa, it is largely used for beef cattle production in Brazil. Brachiaria reproduces sexually or asexually by apomixis, and development of biotechnological tools for gene transfer is being researched to support the breeding programs. The molecular bases of reproduction have not yet been fully elucidated; it is known that gametophyte formation and main reproductive events occur inside the anthers and ovaries. There is therefore much interest in identifying genes expressed in these organs and their corresponding upstream regulatory sequences. In this work we characterized three cDNA from ovaries of B. brizantha plants (CL 09, CL10, and CL21) which show similarity in databases with genes encoding ribosomal proteins S8, S15a, and L41 and were named BbrizRPS8, BbrizRPS15a, and BbrizRPL41, respectively. These clones show higher expression in ovaries, anthers and roots, mitotically active tissues, when compared to leaves of B. brizantha. Localization of transcripts of BbrizRPS8, BbrizRPS15a, and BbrizRPL41 was investigated in the reproductive organs, ovaries, and anthers, from the beginning of development up to maturity. Their activity was higher in early stages of anther development, while expression was detected in all developmental stages in the ovaries, except for BbrizS15a, which was detected only in synergids of apomictic plants.
Assuntos
Brachiaria/crescimento & desenvolvimento , Brachiaria/metabolismo , Flores/metabolismo , Proteínas de Plantas/metabolismo , Proteínas Ribossômicas/metabolismo , Brachiaria/genética , Flores/genética , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Proteínas de Plantas/genética , Proteínas Ribossômicas/genéticaRESUMO
Meloidogyne spp., plant-parasitic nematodes present worldwide, are intensively studied because of the damage caused to a large variety of agronomically important crops. Several reports indicate that proteins from the Meloidogyne spp. dorsal gland might play an important role to allow proper establishment of a functional nematode feeding site. The precise role of these proteins in the process of feeding cell development is unknown. To gain insights into the function of these secreted M. incognita proteins, we constitutively (ectopically) expressed the nematodes dorsal gland protein 7E12 in tobacco plants. It was found that the number of galls at 8 and 16 days after nematode infection was significantly higher in transgenic plants compared to control plants. Eggs from nematodes in transgenic plants hatched faster than those in control plants. Histological analysis of nematode induced galls in transgenic plants clearly shows a different morphology. Giant feeding cells harbor more vacuoles and an increased amount of cell wall invaginations, while neighboring cells surrounding feeding cells are more numerous. These results suggest that the presence of the 7E12 protein in tobacco accelerates gall formation. This assumption is supported by our data illustrating faster gall formation and egg eclosion in transgenic plants.