Interactions Between Jasmonates And Ethylene In The Regulation Of Root Hair Development In Arabidopsis

Root hair is an important model to study cell patterning and differentiation in higher plants. Hormones are involved in the regulation of root hair development. Ethylene and auxin are critical regulators of root hair development. In this study, jasmonates (JAs) were reported to be involved in the regulation of root hair development in Arabidopsis. The role of JAs was examined in Arabidopsis root hair development as well as their interaction with ethylene in this process. Using wild type (WT) and ethylene-insensitive mutants (etr1-1, etr1-3) and ethylene over-producer mutant (etol-l)as materials, the results have showed that both methyl jasmonate (MeJA) and jasmonic acid (JA) had pronounced effects on root hair formation, which both of them can promote root hair formation. The reason of JAs-induced root hair formation was that MeJA had a stimulatory effect on the activation of trichoblast cells for root hair formation. In addition, the induction of branched hair formation may be a novel function of MeJA on root hair development. However, the effects of MeJA and JA on root hair formation were blocked by ethylene inhibitors Ag⁺ or aminoethoxyvinylglycine (AVG). The stimulatory effects of MeJA and JA were also diminished in ethylene-insensitive mutants etr1-1 and etr1-3. Furthermore, JAs biosynthesis inhibitors ibuprofen and salicylhydroxamic acid (SHAM) suppressed 1-aminocyclopropane-1-carboxylic acid (ACC)-induced root hair formation, and decreased the root hairs in seedlings of ethylene over-producer mutant eto1-1. These results suggested that JAs promoted root hair formation, through an interaction with ethylene.Root hair development has been shown to be largely affected by nutrition concentration. Our study found that high rates of ammonium nitrate (NH4NO3) supply stimulated the branched root hair formation; hairs were initiated from a large bulge on the epidermal cells, from which one to three branches emerged, or from the base sides of growing hair cells. Some of these branches underwent further branching. On the other hand, NH4NO3 treatment inhibited root hair elongation. The role of ammonium was stronger than that of the nitrate. Exogenous ACC and IAA treatment prevented NH₄NO₃-induced...