Analysis of Microtubule-Associated-Proteins during IBA-Mediated Adventitious Root Induction Reveals KATANIN Dependent and Independent Alterations of Expression Patterns

Adventitious roots (AR) are post embryonic lateral organs that differentiate from non-root tissues. The understanding of the molecular mechanism which underlies their differentiation is important because of their central role in vegetative plant propagation. Here it was studied how the expression of different microtubule (MT)-associated proteins (MAPs) is affected during AR induction, and whether expression differences are dependent on MT organization itself. To examine AR formation when MTs are disturbed we used two mutants in the MT severing protein KATANIN. It was found that rate and number of AR primordium formed following IBA induction for three days was reduced in bot1-1 and bot1-7 plants. The reduced capacity to form ARs in bot1-1 was associated with altered expression of MAP-encoding genes along AR induction. While the expression of MAP65-4, MAP65-3, AURORA1, AURORA2 and TANGLED, increased in wild-type but not in bot1-1 plants, the expression of MAP65-8 and MDP25 decreased in wild type plants but not in the bot1-1 plant after two days of IBA-treatment. The expression of MOR1 was increased two days after AR induction in wild type and bot1-1 plants. To examine its expression specifically in AR primordium, MOR1 upstream regulatory sequence was isolated and cloned to regulate GFP. Expression of GFP was induced in the primary root tips and lateral roots, in the pericycle of the hypocotyls and in all stages of AR primordium formation. It is concluded that the expression of MAPs is regulated along AR induction and that reduction in KATANIN expression inhibits AR formation and indirectly influences the specific expression of some MAPs.