Abscisic acid (ABA) signaling plays a critical role in regulating root growth and root system architecture. ABA-mediated growth promotion and root tropic response under water stress are key responses ...for plant survival under limiting water conditions. In this work, we have explored the role of Arabidopsis (Arabidopsis thaliana) PYRABACTIN RESISTANCE1 (PYR1)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS for root ABA signaling. As a result, we discovered that PYL8 plays a nonredundant role for the regulation of root ABA sensitivity. Unexpectedly, given the multigenic nature and partial functional redundancy observed in the PYR/PYL family, the single pyl8 mutant showed reduced sensitivity to ABA-mediated root growth inhibition. This effect was due to the lack of PYL8-mediated inhibition of several clade A phosphatases type 2C (PP2Cs), since PYL8 interacted in vivo with at least five PP2Cs, namely HYPERSENSITIVE TO ABA1 (HAB1), HAB2, ABA-INSENSITIVE1 (ABI1), ABI2, and PP2CA/ABA-HYPERSENSITIVE GERMNATION3 as revealed by tandem affinity purification and mass spectrometry proteomic approaches. We also discovered that PYR/PYL receptors and clade A PP2Cs are crucial for the hydrotropic response that takes place to guide root growth far from regions with low water potential. Thus, an ABA-hypersensitive pp2c quadruple mutant showed enhanced hydrotropism, whereas an ABA-insensitive sextuple pyr/pyl mutant showed reduced hydrotropic response, indicating that ABA-dependent inhibition of PP2Cs by PYR/PYLs is required for the proper perception of a moisture gradient.
Genetic incompatibilities resulting from interactions between two loci represent a potential source of postzygotic barriers and may be an important factor in evolution when they impair the outcome of ...interspecific crosses. We show that, in crosses between strains of the plant Arabidopsis thaliana, loci interact epistatically, controlling a recessive embryo lethality. This interaction is explained by divergent evolution occurring among paralogs of an essential duplicate gene, for which the functional copy is not located at the same locus in different accessions. These paralogs demonstrate genetic heterogeneity in their respective evolutionary trajectories, which results in widespread incompatibility among strains. Our data suggest that these passive mechanisms, gene duplication and extinction, could represent an important source of genetic incompatibilities across all taxa.
The regulation of signalling capacity, combined with the spatiotemporal distribution of developmental signals themselves, is pivotal in setting developmental responses in both plants and animals
. ...The hormone auxin is a key signal for plant growth and development that acts through the AUXIN RESPONSE FACTOR (ARF) transcription factors
. A subset of these, the conserved class A ARFs
, are transcriptional activators of auxin-responsive target genes that are essential for regulating auxin signalling throughout the plant lifecycle
. Although class A ARFs have tissue-specific expression patterns, how their expression is regulated is unknown. Here we show, by investigating chromatin modifications and accessibility, that loci encoding these proteins are constitutively open for transcription. Through yeast one-hybrid screening, we identify the transcriptional regulators of the genes encoding class A ARFs from Arabidopsis thaliana and demonstrate that each gene is controlled by specific sets of transcriptional regulators. Transient transformation assays and expression analyses in mutants reveal that, in planta, the majority of these regulators repress the transcription of genes encoding class A ARFs. These observations support a scenario in which the default configuration of open chromatin enables a network of transcriptional repressors to regulate expression levels of class A ARF proteins and modulate auxin signalling output throughout development.
The abscisic acid receptor PYL8 plays an important role for regulation of root abscisic acid sensitivity, and abscisic acid-dependent inhibition of PP2Cs by PYR/PYLs is required for root ...hydrotropism.
Abscisic acid (
ABA
) signaling plays a critical role in regulating root growth and root system architecture.
ABA
-mediated growth promotion and root tropic response under water stress are key responses for plant survival under limiting water conditions. In this work, we have explored the role of Arabidopsis (
Arabidopsis thaliana
) PYRABACTIN RESISTANCE1 (PYR1)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS for root
ABA
signaling. As a result, we discovered that PYL8 plays a nonredundant role for the regulation of root
ABA
sensitivity. Unexpectedly, given the multigenic nature and partial functional redundancy observed in the PYR/PYL family, the single
pyl8
mutant showed reduced sensitivity to
ABA
-mediated root growth inhibition. This effect was due to the lack of PYL8-mediated inhibition of several clade A phosphatases type 2C (
PP2Cs
), since PYL8 interacted in vivo with at least five
PP2Cs
, namely HYPERSENSITIVE TO ABA1 (HAB1), HAB2, ABA-INSENSITIVE1 (ABI1), ABI2, and PP2CA/ABA-HYPERSENSITIVE GERMINATION3 as revealed by tandem affinity purification and mass spectrometry proteomic approaches. We also discovered that PYR/PYL receptors and clade A
PP2Cs
are crucial for the hydrotropic response that takes place to guide root growth far from regions with low water potential. Thus, an
ABA
-hypersensitive
pp2c
quadruple mutant showed enhanced hydrotropism, whereas an
ABA
-insensitive sextuple
pyr/pyl
mutant showed reduced hydrotropic response, indicating that
ABA
-dependent inhibition of
PP2Cs
by PYR/PYLs is required for the proper perception of a moisture gradient.
Cerebrospinal fluid (CSF) concentrations of 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA) and probenecid were examined in 14 children with epilepsy (ages 6 months to 17 years) and 17 ...controls (ages 14 months to 16 years). The concentrations of amine metabolites were significantly correlated with probenecid concentrations in both groups of children. Cerebrospinal fluid concentrations of 5-HIAA were 63.6 ng per milliliter plus or minus 8.23 S.E.M. and 117 ng per milliliter plus or minus 11.6 S.E.M. for the epilepsy and control groups respectively. HVA averaged 89.1 ng per milliliter plus or minus 15.2 S.E.M in epilepsy and 172 ng per milliliter plus or minus 19.2 S.E.M. in the control group. These findings indicate a significant difference between epilepsy and control groups. Probenecid concentrations were similar in each group. The reduced cerebrospinal fluid amine metabolite concentrations in children with epilepsy were not related to age, anticonvulsant medication, cerebrospinal fluid folate or protein concentration, or cerebrospinal fluid cell count. Our findings suggest a relationship between brain amines and epilepsy.
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