Disease relevance of ABI2

• Arabidopsis ABA mutants (aba1 and abi2) displayed reduced Adh mRNA induction levels following either dehydration treatment or exogenous application of ABA [1].

High impact information on ABI2

• The activation is abolished by a CDPK1 mutation in the kinase domain and diminished by a constitutively active protein phosphatase 2C that is capable of blocking responses to the stress hormone abscisic acid [2].
• A protein phosphatase 2C involved in ABA signal transduction in Arabidopsis thaliana [3].
• ABI1, a protein phosphatase 2C, is a key component of signal transduction in ARABIDOPSIS: It regulates diverse responses to the phytohormone abscisic acid (ABA) such as stomatal closure, seed dormancy and inhibition of vegetative growth [4].
• The reduced form of ABI2 was converted to the oxidized form by the addition of oxidized ATGPX3 in vitro, which might mediate ABA and oxidative signaling [5].
• By screening a two-hybrid cDNA library, we isolated a protein phosphatase 2C (AtPP2CA) involved in abscisic acid signaling as a putative partner of AKT2 [6].

Biological context of ABI2

• This demonstrates that the signal transduction pathways for all three stimuli converge on, or close to, the ABI1 and ABI2 gene products [7].
• The deduced amino acid sequence is 55% and 54% identical to ABI1 and ABI2, respectively [8].
• Comparison of the genomic structure of the ABI1, ABI2 and AtP2C-HA genes suggests that they belong to a multigene family [8].
• The data suggest that this mutation localized in a conserved motif in the PP2C catalytic domain could be used in other PP2Cs to reveal their biological functions [9].
• Thus, the homologous ABI1 and ABI2 phosphatases appear to assume partially redundant functions in ABA signaling, which may provide a mechanism to maintain informational homeostasis [10].

Anatomical context of ABI2

• Abscisic acid activation of plasma membrane Ca(2+) channels in guard cells requires cytosolic NAD(P)H and is differentially disrupted upstream and downstream of reactive oxygen species production in abi1-1 and abi2-1 protein phosphatase 2C mutants [11].

Associations of ABI2 with chemical compounds

• Thus, ABI1 and ABI2 seem to control fibrillin expression that is involved in mediating ABA-induced photoprotection [12].
• The interaction between SOS2 and ABI2 was disrupted by the abi2-1 mutation, which causes increased tolerance to salt shock and abscisic acid insensitivity in plants [13].
• In addition, the redox states of both ATGPX3 and ABI2 were found to be regulated by H(2)O(2) [5].
• Upon H2O2 challenge, ABI2 is rapidly inactivated with an IC50 value of 50 microM in the presence of reduced glutathione [14].
• Inhibitor studies with phenylarsine oxide and manipulation of the redox status of ABI2 in vitro indicate that oxidation of critical cysteine residue(s) is responsible for inactivation [14].

Physical interactions of ABI2

• We found that some PKSs interact strongly with ABI2 whereas others interact preferentially with ABI1 [13].
• The AKT3 potassium channel protein interacts with the AtPP2CA protein phosphatase 2C [15].

Other interactions of ABI2

• A novel domain in the protein kinase SOS2 mediates interaction with the protein phosphatase 2C ABI2 [13].
• The phosphatase activity of ABI2, measured in vitro, was reduced approximately fivefold by the addition of oxidized ATGPX3 [5].
• Low-oxygen response was slightly increased in the aba1 mutant but was unchanged in abi2 [1].
• Abscisic acid (ABA) signaling mutants (abi1 and abi2) and the UV-sensitive mutant, uvh6, showed the strongest defects in acquired thermotolerance of root growth and seedling survival [16].
• These findings suggest that there is a separate regulatory pathway independent of ABI2/ ABI4/ ABI5 [17].

Analytical, diagnostic and therapeutic context of ABI2

• Here, we show that phospholipase Dalpha1 (PLDalpha1) mediates the ABA effects on stomata through interaction with a protein phosphatase 2C (PP2C) and a heterotrimeric GTP-binding protein (G protein) in Arabidopsis [18].

References