title: Expression-based and co-localization detection of arabinogalactan protein 6 and arabinogalactan protein 11 interactors in Arabidopsis pollen and pollen tubes.
abstract: BACKGROUND
  Arabinogalactan proteins (AGPs) are cell wall proteoglycans that have been shown to be important for pollen development. An Arabidopsis double null mutant for two pollen-specific AGPs (agp6 agp11) showed reduced pollen tube growth and compromised response to germination cues in vivo. A microarray experiment was performed on agp6 agp11 pollen tubes to search for genetic interactions in the context of pollen tube growth. A yeast two-hybrid experiment for AGP6 and AGP11 was also designed.
  
  
  RESULTS
  The lack of two specific AGPs induced a meaningful shift in the gene expression profile. In fact, a high number of genes showed altered expression levels, strengthening the case that AGP6 and AGP11 are involved in complex phenomena. The expression levels of calcium- and signaling-related genes were found to be altered, supporting the known roles of the respective proteins in pollen tube growth. Although the precise nature of the proposed interactions needs further investigation, the putative involvement of AGPs in signaling cascades through calmodulin and protein degradation via ubiquitin was indicated. The expression of stress-, as well as signaling- related, genes was also changed; a correlation that may result from the recognized similarities between signaling pathways in both defense and pollen tube growth.The results of yeast two-hybrid experiments lent further support to these signaling pathways and revealed putative AGP6 and AGP11 interactors implicated in recycling of cell membrane components via endocytosis, through clathrin-mediated endosomes and multivesicular bodies.
  
  
  CONCLUSIONS
  The data presented suggest the involvement of AGP6 and AGP11 in multiple signaling pathways, in particular those involved in developmental processes such as endocytosis-mediated plasma membrane remodeling during Arabidopsis pollen development. This highlights the importance of endosomal trafficking pathways which are rapidly emerging as fundamental regulators of the wall physiology.
authors.affiliation: Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Edifício FC4 Rua do Campo Alegre, 4169-007, Porto, Portugal.
authors.forename: Mário
authors.initials: M
authors.lastname: Costa
authors.forename: Margarida Sofia
authors.initials: MS
authors.lastname: Nobre
authors.forename: Jörg D
authors.initials: JD
authors.lastname: Becker
authors.forename: Simona
authors.initials: S
authors.lastname: Masiero
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Amorim
authors.forename: Luís Gustavo
authors.initials: LG
authors.lastname: Pereira
authors.forename: Sílvia
authors.initials: S
authors.lastname: Coimbra
mesh_terms: D029681:Arabidopsis Proteins / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D009088:Mucoproteins / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D011058:Pollen / Q000378:metabolism*; D053205:Pollen Tube / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D009088:Mucoproteins; D010940:Plant Proteins; C006619:arabinogalactan proteins