RESUMO
In flowering plants, male gametes (sperm cells) develop within male gametophytes (pollen grains) and are delivered to female gametes for double fertilization by pollen tubes. Therefore, pollen tube growth is crucial for reproduction. The mechanisms that control pollen tube growth remain poorly understood. In this study, we demonstrated that the ARID-HMG DNA-binding protein AtHMGB15 plays an important role in pollen tube growth. This protein is preferentially expressed in pollen grains and pollen tubes and is localized in the vegetative nuclei of the tricellular pollen grains and pollen tubes. Knocking down AtHMGB15 expression via a Ds insertion caused retarded pollen tube growth, leading to a significant reduction in the seed set. The athmgb15-1 mutation affected the expression of 1686 genes in mature pollen, including those involved in cell wall formation and modification, cell signaling and cellular transport during pollen tube growth. In addition, it was observed that AtHMGB15 binds to DNA in vitro and interacts with the transcription factors AGL66 and AGL104, which are required for pollen maturation and pollen tube growth. These results suggest that AtHMGB15 functions in pollen tube growth through the regulation of gene expression.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica de Plantas , Transdução de Sinais , Arabidopsis/citologia , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/fisiologia , Proteínas de Arabidopsis/metabolismo , Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/metabolismo , Dimerização , Fertilização , Perfilação da Expressão Gênica , Genes Reporter , Mutação , Análise de Sequência com Séries de Oligonucleotídeos , Especificidade de Órgãos , Fenótipo , Pólen/genética , Pólen/crescimento & desenvolvimento , Pólen/fisiologia , Tubo Polínico/genética , Tubo Polínico/crescimento & desenvolvimento , Tubo Polínico/fisiologia , Polinização , Mapeamento de Interação de Proteínas , Reprodução , Sementes/genética , Sementes/crescimento & desenvolvimento , Sementes/fisiologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
The cell wall is important for pollen tube growth, but little is known about the molecular mechanism that controls cell wall deposition in pollen tubes. Here, the functional characterization of the pollen-expressed Arabidopsis cellulose synthase-like D genes CSLD1 and CSLD4 that are required for pollen tube growth is reported. Both CSLD1 and CSLD4 are highly expressed in mature pollen grains and pollen tubes. The CSLD1 and CSLD4 proteins are located in the Golgi apparatus and transported to the plasma membrane of the tip region of growing pollen tubes, where cellulose is actively synthesized. Mutations in CSLD1 and CSLD4 caused a significant reduction in cellulose deposition in the pollen tube wall and a remarkable disorganization of the pollen tube wall layers, which disrupted the genetic transmission of the male gametophyte. In csld1 and csld4 single mutants and in the csld1 csld4 double mutant, all the mutant pollen tubes exhibited similar phenotypes: the pollen tubes grew extremely abnormally both in vitro and in vivo, which indicates that CSLD1 and CSLD4 are not functionally redundant. Taken together, these results suggest that CSLD1 and CSLD4 play important roles in pollen tube growth, probably through participation in cellulose synthesis of the pollen tube wall.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Celulose/metabolismo , Glucosiltransferases/metabolismo , Tubo Polínico/crescimento & desenvolvimento , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Glucosiltransferases/genética , Pólen/genética , Pólen/metabolismo , Tubo Polínico/genética , Tubo Polínico/metabolismoRESUMO
In flowering plants, male gametes are delivered to female gametophytes by pollen tubes. Although it is important for sexual plant reproduction, little is known about the genetic mechanism that controls pollen germination and pollen tube growth. Here we report the identification and characterization of two novel mutants, gnom-like 2-1 (gnl2-1) and gnl2-2 in Arabidopsis thaliana, in which the pollen grains failed to germinate in vitro and in vivo. GNL2 encodes a protein homologous to the adenosine diphosphate-ribosylation factor-guanine nucleotide exchange factors, GNOM and GNL1 that are involved in endosomal recycling and endoplasmic reticulum-Golgi vesicular trafficking. It was prolifically expressed in pollen grains and pollen tubes. The results of the present study suggest that GNL2 plays an important role in pollen germination.