RESUMO

The plant vascular system plays a pivotal role in the delivery of nutrients to distantly located organs. Recent discoveries have provided new insight into a novel role for plasmodesmata and the phloem in terms of the transport and delivery of information macromolecules (i.e. proteins and ribonucleoprotein complexes). Non-cell/organ-autonomous control over gene expression may function both in defense signaling and developmental programming in plants.

Assuntos

Comunicação Celular , Inativação Gênica , Fenômenos Fisiológicos Vegetais , RNA de Plantas/metabolismo , Transporte Biológico/fisiologia , Regulação da Expressão Gênica de Plantas , Substâncias Macromoleculares , Proteínas de Plantas/metabolismo , Processamento Pós-Transcricional do RNA

RESUMO

Sucrose-phosphate synthase (SPS) is one of the key regulatory enzymes in carbon assimilation and partitioning in plants. SPS plays a central role in the production of sucrose in photosynthetic cells and in the conversion of starch or fatty acids into sucrose in germinating seeds. To explore the mechanisms that regulate the tissue-specific and developmental distribution of SPS, the expression pattern of rice (Oryza sativa) sps1 (GenBank accession no. U33175) was examined by in situ reverse transcriptase-polymerase chain reaction and the expression directed by the sps1 promoter using the beta-glucuronidase reporter gene. It was found that the expression of the rice sps1 gene is limited to mesophyll cells in leaves, the scutellum of germinating seedlings, and pollen of immature inflorescences. During leaf development, the sps1 promoter directs a basipetal pattern of expression that coincides with the distribution of SPS activity during the leaf sink-to-source transition. It was also found that during the vegetative part of the growth cycle, SPS expression and enzymatic activity are highest in the youngest fully expanded leaf. Additionally, it was observed that the expression of the sps1 promoter is regulated by light and dependent on plastid development in photosynthetic tissues, whereas expression in scutellum is independent of both light and plastid development.

Assuntos

Genes de Plantas , Glucosiltransferases/genética , Oryza/crescimento & desenvolvimento , Oryza/genética , Sequência de Bases , DNA de Plantas/genética , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Glucuronidase/genética , Dados de Sequência Molecular , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA de Plantas/genética , RNA de Plantas/metabolismo , Distribuição Tecidual