C-terminal domain phosphatase-like family members (AtCPLs) differentially regulateArabidopsis thalianaabiotic stress signaling, growth, and development

Abstract

Cold, hyperosmolarity, and abscisic acid (ABA) signaling induce RD29A expression, which is an indicator of the plant stress adaptation response. Two nonallelic Arabidopsis thaliana (ecotype C24) T-DNA insertional mutations, cpl1 and cpl3, were identified based on hyperinduction of RD29A expression that was monitored by using the luciferase (LUC) reporter gene (RD29A::LUC) imaging system. Genetic linkage analysis and complementation data established that the recessive cpl1 and cpl3 mutations are caused by T-DNA insertions in AtCPL1 (Arabidopsis C-terminal domain phosphatase-like) and AtCPL3, respectively. Gel assays using recombinant AtCPL1 and AtCPL3 detected innate phosphatase activity like other members of the phylogenetically conserved family that dephosphorylate the C-terminal domain of RNA polymerase II (RNAP II). cpl1 mutation causes RD29A::LUC hyperexpression and transcript accumulation in response to cold, ABA, and NaCl treatments, whereas the cpl3 mutation mediates hyperresponsiveness only to ABA. Northern analysis confirmed that LUC transcript accumulation also occurs in response to these stimuli. cpl1 plants accumulate biomass more rapidly and exhibit delayed flowering relative to wild type whereas cpl3 plants grow more slowly and flower earlier than wild-type plants. Hence AtCPL1 and AtCPL3 are negative regulators of stress responsive gene transcription and modulators of growth and development. These results suggest that C-terminal domain phosphatase regulation of RNAP II phosphorylation status is a focal control point of complex processes like plant stress responses and development. AtCPL family members apparently have both unique and overlapping transcriptional regulatory functions that differentiate the signal output that determines the plant response. P lants tolerate environmental stress because of numerous physiological adaptations, which have been attributed to the function of various determinant genes (1). In Arabidopsis thaliana, transcription of RD (Responsive to Dehydration) (2) and COR (Cold Responsive) (3) genes is activated by cold or hyperosmotic stress. The plant hormone abscisic acid (ABA) activates transcription of some RD and COR genes through an interaction involving the cis element ABRE (ABA-responsive element) and basic leucine zipper transcription factors such as ABFs͞AREBs (4, 5). However, expression of some RD or COR genes is activated by low temperature or desiccation, independent of ABA, by the interaction of CBF͞DREB DNA-binding proteins with another cis element, DRE (6, 7). Overexpression of CBF͞DREB in transgenic Arabidopsis plants induces ectopic expression of RD͞COR genes and confers desiccation and cold tolerance (7,8).Recent genetic dissection of cold-, hyperosmolarity-, and ABA-induced signaling that regulates gene expression and adaptation indicates that the cascade signature is modulated by numerous positive and negative regulators (9-14). Signaling control of plant gene expression is known now to include components that function at various stages in mRNA metaboli...

Repression of stress-responsive genes by FIERY2, a novel transcriptional regulator in Arabidopsis

“…Allelism tests found six new fry2 alleles, which were named as fry2-2 through fry2-7. Quantitation of luminescence expression in these mutants indicates that the average luminescence intensities in these mutants are [11][12][13][14][15][16][17][18][19][20][8][9][10][11], and 15-21 times higher than those in the wild type under cold, ABA, and NaCl treatments, respectively. The intensities for the nonstress control treatment are only 1.6-4.1 times higher in fry2 mutants than in the wild type (data not shown).…”

Arabidopsis C-terminal domain phosphatase-like 1 and 2 are essential Ser-5-specific C-terminal domain phosphatases

“…For reciprocal cross analysis, a fry2-1͞ϩ cpl2-2͞ϩ plant and a fry2-1 plant were used as parents. F 1 seedlings with homozygous fry2-1 genotype were selected by using RD29a-LUC expression after cold and ABA treatments as described (5,6). The fry2-1 phenotype of the F 1 plants indicated that the gametes from the diheterozygous parent contained the fry2-1 chromosome.…”

“…The stress-inducible promoter of the RD29a gene contains dehydration͞cold-responsive elements and ABA-responsive elements that are the targets of distinct families of DNA binding transcription factors (1,2). The plant stress response is also regulated by proteins that impact the core RNA polymerase II (Pol II) transcriptional machinery, the mRNA maturation process, and chromatin structure (3)(4)(5)(6)(7)(8)(9). Analysis of Arabidopsis mutants that display hyperinduction of RD29a expression under stress conditions have identified a family of C-terminal domain (CTD) phosphatase-like (CPL) genes that negatively regulate stressresponsive transcription (5,6).…”

“…The plant stress response is also regulated by proteins that impact the core RNA polymerase II (Pol II) transcriptional machinery, the mRNA maturation process, and chromatin structure (3)(4)(5)(6)(7)(8)(9). Analysis of Arabidopsis mutants that display hyperinduction of RD29a expression under stress conditions have identified a family of C-terminal domain (CTD) phosphatase-like (CPL) genes that negatively regulate stressresponsive transcription (5,6). The CPL1 and CPL3 genes discovered in the screen for hyperinduction are so named because they encode large polypeptides (967 and 1,241 aa, respectively) with local primary structure similarity to the Fcp1 family of fungal and metazoan protein serine phosphatases, which regulate transcription by dephosphorylating the CTD of the largest subunit of RNA Pol II (10).…”

The STT3a Subunit Isoform of the Arabidopsis Oligosaccharyltransferase Controls Adaptive Responses to Salt/Osmotic Stress

“…Seedlings were transferred to basal medium supplemented with 160 mM NaCl or various concentrations of other compounds, and root growth was scored 8 days later. RD29a-LUC expression was monitored with a charge-coupled device imaging system (Roper Scientific, Trenton, NJ) after seedlings were subjected to cold (0ЊC, 2 days), abscisic acid (100 M, 4 h), or NaCl (300 mM, 4 h) treatment (Ishitani et al, 1997;Koiwa et al, 2002).…”