ABSTRACT
AtGRP3 is a glycine-rich protein (GRP) from Arabidopsis thaliana shown to interact with the receptor-like kinase AtWAK1 in yeast, in vitro and in planta. In this work, phenotypic analyses using transgenic plants were performed in order to better characterize this GRP. Plants of two independent knockout alleles of AtGRP3 develop longer roots suggesting its involvement in root size determination. Confocal microscopy analysis showed an abnormal cell division and elongation in grp3-1 knockout mutants. Moreover, we also show that grp3-1 exhibits an enhanced Aluminum (Al) tolerance, a feature also described in AtWAK1 overexpressing plants. Together, these results implicate AtGRP3 function root size determination during development and in Al stress.
Subject(s)
Arabidopsis Proteins/genetics , Arabidopsis/genetics , Membrane Proteins/genetics , Plant Roots/genetics , Protein Kinases/genetics , Aluminum/toxicity , Arabidopsis/anatomy & histology , Arabidopsis/growth & development , Arabidopsis Proteins/biosynthesis , Gene Expression Regulation, Plant , Gene Knockout Techniques , Membrane Proteins/biosynthesis , Microscopy, Confocal , Plant Roots/anatomy & histology , Plant Roots/growth & development , Plants, Genetically Modified/drug effects , Plants, Genetically Modified/genetics , Protein Kinases/biosynthesisABSTRACT
The AtGRP5 gene from Arabidopsis thaliana encodes a glycine-rich protein which has a major activity in protoderm-derived cells and is expressed in cells that undergo the first anatomical modifications leading to somatic embryo development. It has been previously demonstrated that its minimum promoter is 316 bp long including the 5'UTR and presents three putative TATA-boxes sequences and several regions that are homologous to previous characterized cis-acting elements. In order to better characterize the AtGRP5 expression and to identify the promoter regions involved in its preferential epidermal expression, in situ hybridization and 5' promoter deletions were employed. In situ hybridization and GUS expression assays indicate that, besides being present during somatic embryogenesis, AtGRP5 is also expressed during the zygotic embryo development. The sequential 5' deletions indicate that multiple negative and positive regulatory elements are present in the AtGRP5 promoter and operate in order to confer its distinct expression pattern. A 44-bp region was shown to be essential for the epidermal expression of this gene in leaves, stems, flowers and fruits, and is also responsible for high activity of the AtGRP5 promoter in zygotic embryos. An element responsible for the phloem expression was also identified in a 35-bp region.
Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/genetics , Gene Expression Regulation, Plant , Promoter Regions, Genetic , Arabidopsis/embryology , Arabidopsis/metabolism , Arabidopsis Proteins/genetics , Gene Deletion , Gene Expression Regulation, Developmental , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , TATA Box , Nicotiana/genetics , Nicotiana/metabolismABSTRACT
Although several glycine-rich protein (GRP) genes were isolated and characterized, very little is known about their function. The primary structure of AtGRP5 from Arabidopsis thaliana has a signal peptide followed by a region with high glycine content. In this work, green fluorescent protein fusions were obtained in order to characterize the sub-cellular localization of the AtGRP5 protein. The results indicated that this protein is the first described vacuolar GRP. Sense, antisense and RNAi transgenic A. thaliana plants were generated and analyzed phenotypically. Plants overexpressing AtGRP5 showed longer roots and an enhanced elongation of the inflorescence axis, while antisense and RNAi plants demonstrated the opposite phenotype. The analysis of a knockout T-DNA line corroborates the phenotypes obtained with the antisense and RNAi plants. Altogether, these results suggest that this vacuolar GRP could be involved in organ growth by promoting cell elongation processes.
Subject(s)
Arabidopsis Proteins/physiology , Arabidopsis/metabolism , Cell Shape/physiology , Glycine/chemistry , Plants, Genetically Modified/metabolism , Vacuoles/metabolism , Arabidopsis/cytology , Arabidopsis/genetics , Arabidopsis/growth & development , Arabidopsis Proteins/genetics , Cell Shape/genetics , DNA, Bacterial/genetics , Gene Expression Regulation, Plant/genetics , Gene Expression Regulation, Plant/physiology , Microscopy, Confocal , Plants, Genetically Modified/genetics , Plants, Genetically Modified/growth & development , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
The occurrence of quasi-repetitive glycine-rich peptides has been reported in different organisms. Glycine-rich regions are proposed to be involved in protein-protein interactions in some mammalian protein families. In plants, a set of glycine-rich proteins (GRPs) was characterized several years ago, and since then a wealth of new GRPs have been identified. GRPs may have very diverse sub-cellular localization and functions. The only common feature among all different GRPs is the presence of glycine-rich repeat domains. The expression of genes encoding GRPs is developmentally regulated, and also induced, in several plant genera, by physical, chemical and biological factors. In addition to the highly modulated expression, several GRPs also show tissue-specific localization. GRPs specifically expressed in xylem, phloem, epidermis, anther tapetum and roots have been described. In this paper, the structural and functional features of these proteins in Eucalyptus are summarized. Since this is the first description of GRPs in this species, particular emphasis has been given to the expression pattern of these genes by analyzing their abundance and prevalence in the different cDNA-libraries of the Eucalyptus Genome Sequencing Project Consortium (ForEST). The comparison of GRPs from Eucalyptus and other species is also discussed
