BioProject

Although the nucleolus is known to be involved in the plant stress response, the underlying mechanisms remain unclear. In the present study, we genetically isolated and characterized the Arabidopsis thaliana salt hypersensitive mutant 1 (sahy1), which exhibits slow growth, short roots, and sterility. SAHY1 encodes an unknown protein that is predominantly expressed in root tips and mature pollens. Subcellular localization further demonstrated that SAHY1 is a nucleolar protein. Ploidy analysis and detection of S-phase cell cycle progression indicated that mitosis is reduced in the root tips of sahy1 plants. Furthermore, levels of reactive oxygen species (ROS) are reduced in the mutant. In addition to exhibiting changes in venation pattern, palisade mesophyll cells, the auxin response, and fertility, the sahy1 mutant is resistant to the protein translation inhibitors, streptomycin and cycloheximide, and has altered expression profiles of ribosome-related genes, reflecting the involvement of SAHY1 in ribosome assembly. Using a combination of transcriptome and gene coexpression clustering analyses, we identified a striking functional module in which SPIRAL 1-LIKE 4 (SPL4), which encodes a microtubule-localized protein, mediates the salt response that acts by modulating dynamic microtubule instability. Supporting evidence indicates that sahy1 is resistant to a microtubule-destabilizing drug (oryzalin), that the cortical microtubule array in sahy1 exhibits changes in dynamic instability, and that the spr1/spl2/spl3/spl4 quadruple mutant is oversensitive to salt. Collectively, these data demonstrate that a novel nucleolar protein, SAHY1, plays critical roles in salt sensitivity, plant growth, and development by integrating the diverse functions of its downstream genes. As the sahy1 mutant plants showed slow growth, short roots, and sterility, the aim of this experiment is to examine gene expression profile in root tissues mediated by SAHY1. The data obtained from this study was compared with chip database derived from root tissues and performed an analysis of gene coexpression clustering. Overall design: included, are there control and/or reference Samples, etc...Arabidopsis seeds were grown on basal medium for five days, transferred to fresh medium and grown vertically for another seven days. After the 12-day culture, the roots were removed and used for RNA extraction. Ten micrograms of total RNA was used for cDNA synthesis and labeled by in vitro transcription. Eleven micrograms of labeled sample was hybridized to Affymetrix ATH1 GeneChips at 45oC for 16.5 h. Samples were washed and stained using a Fluidic Station-450, and the ATH1 chips were scanned with an Affymetrix GeneChip Scanner 7G. Data analysis was performed using GeneSpring GX 10.0.1 software (Agilent). Statistical analysis included a cut-off value of P<0.05, T-test unpaired, asymptotic p-value computation, and multiple testing correction by Benjamini-Hochberg FDR (1995). The microarray analysis was performed in biological triplicate.