Genome-wide gene expression profiling inArabidopsis thalianareveals new targets of abscisic acid and largely impaired gene regulation in theabi1-1mutant

Abstract

The phytohormone abscisic acid (ABA) plays important regulatory roles in many plant developmental processes including seed dormancy, germination,growth, and stomatal movements. These physiological responses to ABA are in large part brought about by changes in gene expression. To study genome-wide ABA-responsive gene expression we applied massively parallel signature sequencing (MPSS) to samples from Arabidopsis thaliana wildtype (WT)and abi1-1 mutant seedlings. We identified 1354 genes that are either up- or downregulated following ABA treatment of WT seedlings. Among these ABA-responsive genes, many encode signal transduction components. In addition,we identified novel ABA-responsive gene families including those encoding ribosomal proteins and proteins involved in regulated proteolysis. In the ABA-insensitive mutant abi1-1, ABA regulation of about 84.5% and 6.9%of the identified genes was impaired or strongly diminished, respectively;however, 8.6% of the genes remained appropriately regulated. Compared to other methods of gene expression analysis, the high sensitivity and specificity of MPSS allowed us to identify a large number of ABA-responsive genes in WT Arabidopsis thaliana. The database given in our supplementary materialprovides researchers with the opportunity to rapidly assess whether genes of interest may be regulated by ABA. Regulation of the majority of the genes by ABA was impaired in the ABA-insensitive mutant abi1-1. However, a subset of genes continued to be appropriately regulated by ABA, which suggests the presence of at least two ABA signaling pathways, only one of which is blocked in abi1-1.

Overexpression of AtMYB44 Enhances Stomatal Closure to Confer Abiotic Stress Tolerance in Transgenic Arabidopsis

“…Salt induction of AtHB-7 and AtHB-12, which are regulated by ABI1 in ABA signaling (Hoth et al, 2002), was also decreased (Supplemental Table S3). In addition, salt-induced expression of the genes encoding proteins involved in flavonoid biosynthesis, such as CHS, DFR, and F3H, was lower in 35S:AtMYB44 plants than in wild-type plants.…”

Phosphorylation of the 12 S globulin cruciferin in wild-type and abi1-1 mutant Arabidopsis thaliana (thale cress) seeds

“…The ABI1 locus encodes a unique type of protein phosphatase in that the C-terminal domain possesses serine/ threonine protein phosphatase activity similar to that of PP2Cs (class 2C phosphatases), whereas the N-terminal domain contains a calcium-binding EF-hand motif that generally occurs only in the heterodimeric PP2B-type serine/threonine phosphatases. A single point mutation in the abi1-1 mutant significantly reduces PP2C activity [29,30], and genome-wide gene expression profiling indicates that ABA gene regulation is impaired [45]. Although recombinant fusion proteins containing either the whole ABI1 protein or only the phosphatase domain display in vitro phosphatase activity towards 32 P-labelled casein [46,47]; the in vivo targets have not yet been identified.…”

Enhancement of Abscisic Acid Sensitivity and Reduction of Water Consumption in Arabidopsis by Combined Inactivation of the Protein Phosphatases Type 2C ABI1 and HAB1

“…ABA regulation of the transpiration flow through stomatal pores is a crucial response of the plant to water deficit, as exemplified by the wilty phenotype of both ABA-deficient and ABA-insensitive mutants (Zeevaart and Creelman, 1988). Additionally, the ABA-dependent signaling pathway regulates stressinducible gene expression, leading to a coordinated remodeling of gene expression that affects more than 1,000 genes of the plant transcriptome (Hoth et al, 2002;Seki et al, 2002;Takahashi et al, 2004).…”