Proteomic analysis of chloroplast biogenesis (clb) mutants uncovers novel proteins potentially involved in the development of Arabidopsis thaliana chloroplasts.

Plant cells outstand for their ability to generate biomass from inorganic sources, this phenomenon takes place within the chloroplasts. The enzymatic machinery and developmental processes of chloroplasts have been subject of research for several decades, and this has resulted in the identification of a plethora of proteins that are essential for their development and function. Mutant lines for the genes that code for those proteins, often display pigment-accumulation defects (e.g., albino phenotypes). Here, we present a comparative proteomic analysis of four chloroplast-biogenesis affected mutants (cla1-1, clb2, clb5, clb19) aiming to identify novel proteins involved in the regulation of chloroplast development in Arabidopsis thaliana. We performed 2D-PAGE separation of the protein samples. These samples were then analyzed by computational processing of gel images in order to select protein spots with abundance shifts of at least twofold, statistically significant according to Student's t-test (P<0.01). These spots were subjected to MALDI-TOF mass-spectrometry for protein identification. This process resulted in the discovery of three novel proteins potentially involved in the development of A. thaliana chloroplasts, as their associated mutant lines segregate pigment-deficient plants with abnormal chloroplasts, and altered mRNA accumulation of chloroplast-development marker genes. BIOLOGICAL SIGNIFICANCE: This report highlights the potential of using a comparative proteomics strategy for the study of biological processes. Particularly, we compared the proteomes of wild-type seedlings and four mutant lines of A. thaliana affected in chloroplast biogenesis. From this proteomic analysis it was possible to detect common mechanisms in the mutants to respond to stress and cope with heterotrophy. Notably, it was possible to identify three novel proteins potentially involved in the development or functioning of chloroplasts, also it was demonstrated that plants annotated to carry T-DNA insertions in the cognate genes display pigment-deficient phenotypes, aberrant and underdeveloped chloroplasts, as well as altered mRNA accumulation of chloroplast biogenesis marker genes.

Arabidopsis thaliana mitogen-activated protein kinase 6 is involved in seed formation and modulation of primary and lateral root development.

Mitogen-activated protein kinase (MAPKs) cascades are signal transduction modules highly conserved in all eukaryotes regulating various aspects of plant biology, including stress responses and developmental programmes. In this study, we characterized the role of MAPK 6 (MPK6) in Arabidopsis embryo development and in post-embryonic root system architecture. We found that the mpk6 mutation caused altered embryo development giving rise to three seed phenotypes that, post-germination, correlated with alterations in root architecture. In the smaller seed class, mutant seedlings failed to develop the primary root, possibly as a result of an earlier defect in the division of the hypophysis cell during embryo development, but they had the capacity to develop adventitious roots to complete their life cycle. In the larger class, the MPK6 loss of function did not cause any evident alteration in seed morphology, but the embryo and the mature seed were bigger than the wild type. Seedlings developed from these bigger seeds were characterized by a primary root longer than that of the wild type, accompanied by significantly increased lateral root initiation and more and longer root hairs. Apparently, the increment in primary root growth resulted from an enhanced cell production and cell elongation. Our data demonstrated that MPK6 plays an important role during embryo development and acts as a repressor of primary and lateral root development.

Data for a comparative proteomic analysis of chloroplast biogenesis (clb) mutants.

This data article contains data related to the research article titled Proteomic analysis of chloroplast biogenesis (clb) mutants uncovers novel proteins potentially involved in the development of Arabidopsis thaliana chloroplasts (de Luna-Valdez et al., 2014) [1]. This research article describes the 2-D PAGE-based proteomic analysis of wild-type and four mutant lines (cla1-1, clb2, clb5 and clb19) affected in the development of Arabidopsis thaliana chloroplasts. The report concludes with the discovery of three proteins potentially involved in chloroplast biogenesis. The information presented here represent the tables and figures that detail the processing of the raw data obtained from the image analysis of the 2-D PAGE gels.