Abstract
Root hair formation is induced in lettuce seedlings when they are transferred from pH 6 to pH 4 medium. In future hair-forming cells, transverse cortical microtubule (CMT) arrays randomize before root hairs form. CMT randomization is necessary for root hair initiation and it is induced by ethylene and auxin. Recently, it became clear that abscisic acid (ABA) also induced root hair initiation. Here, we examined the relationship between ABA and CMT randomization, and the crosstalk between ABA and auxin or ethylene during CMT randomization.
Addition of ABA induced CMT randomization and root hairs formed at pH 6. However, when ABA was applied together with inhibitors of ethylene or auxin, neither CMT randomization nor root hair initiation occurred. Addition of ABA biosynthesis inhibitor abamine inhibited CMT randomization and root hair initiation at pH 4. These results suggest that although ABA promotes CMT randomization, ABA itself can not induce it. ABA may induce CMT randomization in cooperation with ethylene and auxin. To make their relationship clearer, we are now observing CMTs in seedlings treated with abamine plus ethylene or auxin at pH 4. The results will also be reported.
