Hu R, Zhu Y, Shen G, Zhang H

TAP46 is a protein phosphatase 2A (PP2A)-associated protein that regulates PP2A activity in Arabidopsis. To study how PP2A is involved in abscisic acid (ABA) signaling in plants, we studied the function of TAP46 in ABA regulated seed maturation and seedling development. Expression of TAP46 coincides with the action of ABA ...

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in developing seeds and during seed germination, and the TAP46 transcript reaches to the highest level in mature seeds. Real-time PCR analysis indicates that external ABA can increase TAP46 transcript level transiently during seed germination. Overexpression of TAP46 increases plant sensitivity to ABA, while tap46 knock-down mutants are less sensitive to ABA during seed germination, suggesting that TAP46 functions positively in ABA signaling. Overexpression of TAP46 also leads to lower PP2A activity, while tap46-1 knock-down mutant displays higher PP2A activity, suggesting that TAP46 negatively regulates PP2A activity in Arabidopsis. Both TAP46 and PP2A interact with the ABA regulated transcription factor ABI5 in vivo, and TAP46's binding to ABI5 can stabilize ABI5. Furthermore, TAP46's binding to the phosphorylated ABI5 may prevent PP2A or PP2A-like phosphatases from removing the phosphate from ABI5, thereby maintaining ABI5 in its active form. Overexpression of TAP46 and inhibition of activities of PP2A or PP2A-like phosphatases can increase transcript levels of several ABI5 regulated genes, suggesting that TAP46 is a positive factor in the ABA regulated gene expression in Arabidopsis.

Date: Dec. 19, 2013

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