Involvement of G1-to-S transition and AhAUX-dependent auxin transport in abscisic acid-induced inhibition of lateral root primodia initiation in Arachis hypogaea L.

Previous study indicated that increasing endogenous abscisic acid (ABA) level could inhibit the lateral root (LR) formation of peanuts. In this study, we investigated the mechanisms by which ABA regulated lateral root primordia (LRP) initiation in peanuts (Arachis hypogaea L). Results suggested that ABA inhibited LRP initiation through blocking G1-to-S transition in seedlings and mature roots: e.g. 5.8% increase in the proportion of G1 phase and 18% decrease in the proportion of S phase after ABA treatment for 6 days. Further study of the expression of the cell cycle marker gene for G2-to-M transition in peanut roots suggested that AhCYCB1 expression was regulated by ABA. We also investigated the cooperative regulation of LRP initiation by ABA and indole-3-acetic acid (IAA). ABA treatment greatly reduced the effects of endogenous IAA on mature roots. The expression of the IAA polar transport gene AhAUX1 appeared to be regulated by ABA since ABA inhibited auxin-mediated LRP initiation by suppressing AhAUX-dependent auxin transport in peanut roots. We further examined the effect of ABA on the expression of DR5::GUS and AtAUX1 in the model plant Arabidopsis. The results of Arabidopsis were consistent with that of the peanut.