ABA mediates PEG-mediated premature differentiation of root apical meristem in plants.

Root apical meristem (RAM) is central for indeterminate growth of plant roots and in sensing environmental stimuli, such as water status. Recently, we reported that PEG8000-simulated mild and moderate osmotic stress induces premature differentiation of RAM, which is a conserved adaptive mechanism in higher plants to cope with water stress. Microarray data analysis revealed that the ABA signaling pathway may be involved in water stress-induced RAM premature differentiation. Here we showed that in wheat, ABA contents increased under water stress with the highest level of ABA in the RAM. Exogenous ABA also induces RAM premature differentiation in both wheat and Arabidopsis plants. Further genetic analysis revealed that loss of function mutations in ABA2 and ABA receptors significantly reduced the level of root tip swelling and RAM premature differentiation in response to PEG-simulated water stress. Together, the results suggest that ABA participates in regulation of PEG-mediated premature differentiation of RAM.