RESUMO
Gibberellins are phytohormones with many roles, including the regulation of fruit development. However, little is known about the relationship between GA perception and fleshy fruit ontogeny, and particularly locule formation. We characterized the expression of cucumber (Cucumis sativus) GA receptor gene (CsGID1a) using quantitative real-time PCR, in situ hybridization and a promoter::ß-glucuronidase (GUS) assay. CsGID1a-RNAi cucumber fruits were observed by dissecting microscope, scanning electron microscopy and transmission electron microscopy. Finally, genome-wide gene expression in young fruits from a control and the RNAi line was compared using a digital gene expression (DGE) analysis approach. The expression pattern of CsGID1a was found to be closely correlated with fruit locule formation, and silencing CsGID1a in cucumber resulted in fruits with abnormal carpels and locules. Overexpression of CsGID1a in the Arabidopsis thaliana double mutant (gid1a gid1c) resulted in 'cucumber locule-like' fruits. The DGE analysis suggested that expression of genes related to auxin synthesis and transport, as well as the cell cycle, was altered in CsGID1a-RNAi fruits, a result that was supported by comparing the auxin content and cellular structures of the control and transgenic fruits. This study demonstrates a previously uncharacterized GA signaling pathway that is essential for cucumber fruit locule formation.
Assuntos
Cucumis sativus/metabolismo , Frutas/genética , Inativação Gênica , Giberelinas/metabolismo , Proteínas de Plantas/metabolismo , Receptores de Superfície Celular/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Cucumis sativus/efeitos dos fármacos , Cucumis sativus/genética , Cucumis sativus/ultraestrutura , Flores/efeitos dos fármacos , Flores/genética , Flores/ultraestrutura , Frutas/efeitos dos fármacos , Frutas/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Inativação Gênica/efeitos dos fármacos , Giberelinas/farmacologia , Glucuronidase/metabolismo , Ácidos Indolacéticos/metabolismo , Mutação/genética , Fenótipo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Receptores de Superfície Celular/química , Homologia de Sequência de AminoácidosRESUMO
Most land plants have a wax layer which covers their aerial parts to protect them from environmental stresses, such as drought, UV radiation, and pathogenic invasion. The wax biosynthesis has been well studied previously in Arabidopsis, but it still remains elusive in cucumber. Here, we isolated a CER1 homolog CsCER1 in cucumber, and we found that the expression of CsCER1 in the cucumber line 3401 which shows waxy fruit phenotype is much higher than that in the cucumber line 3413 which displays glossy fruit phenotype. Spatial and temporal expression analyses revealed that CsCER1 is specifically expressed in the epidermis where waxes are synthesized, and sub-cellular location showed that CsCER1 protein is localized to the endoplasmic reticulum. The expression of CsCER1 can be induced by low temperature, drought, salt stress and abscisic acid. In addition, abnormal expressions of CsCER1 in transgenic cucumber plants have dramatic effects on very-long-chain (VLC) alkanes biosynthesis, cuticle permeability, and drought resistance. Our data suggested that CsCER1 plays an important role in VLC alkanes biosynthesis in cucumber.
Assuntos
Alcanos/metabolismo , Cucumis sativus/genética , Cucumis sativus/fisiologia , Genes de Plantas , Aclimatação/genética , Aclimatação/fisiologia , Alcanos/química , Sequência de Aminoácidos , Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Arabidopsis/genética , Secas , Expressão Gênica , Dados de Sequência Molecular , Permeabilidade , Fenótipo , Filogenia , Epiderme Vegetal/fisiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/fisiologia , Interferência de RNA , Homologia de Sequência de Aminoácidos , Ceras/química , Ceras/metabolismoRESUMO
Cuticular waxes play an important part in protecting plant aerial organs from biotic and abiotic stresses. In previous studies, the biosynthetic pathway of cuticular waxes and relative functional genes has been researched and understood; however, little is known in cucumber (Cucumis sativus L.). In this study, we cloned and characterized an AtWAX2 homolog, CsWAX2, in cucumber and found that it is highly expressed in the epidermis, where waxes are synthesized, while subcellular localization showed that CsWAX2 protein is localized to the endoplasmic reticulum (ER). The transcriptional expression of CsWAX2 was found to be induced by low temperature, drought, salt stress and ABA, while the ectopic expression of CsWAX2 in an Arabidopsis wax2 mutant could partially complement the glossy stem phenotype. Abnormal expression of CsWAX2 in transgenic cucumbers specifically affected both very long chain (VLC) alkanes and cutin biosynthesis. Furthermore, transgenic cucumber plants of CsWAX2 showed significant changes in pollen viability and fruit resistance to water loss and pathogens compared with the wild type. Collectively, these results indicated that CsWAX2 plays a pivotal role in wax biosynthesis, influencing pollen fertility and the plant's response to biotic and abiotic stresses.