Regulation Of Guard Mother Cell Symmetric Division By 1-Aminocvclopropane-1-Carboxylateacid

Previous studies have found that ethylene promotes asymmetric divisions of stomatal lineage cells and terminal symmetric divisions of guard mother cells.In addition,ethylene regulates the differentiation of guard cells.This study observed and analysed stomatal phenotype of abaxial cotyledons epidermis in Col(gll)(which are treated with ethylene-related compounds),ethylene-related and stomatal symmetric division-related mutants by DAPI staining,PI staining,transparency treatment and qRT-PCR.Aimed to analysis the molecular mechanism of ACC-mediated GMC division.The main results are as follows:1.AVG(Aminoethoxyvinylglycine)treatment resulted in the disruption of GMC terminal division and formation of SGCs(Single Guard Cells)in the abaxil cotyledon epidermis of wild type Arabidopsis.In consistant with this,loss of function of ACC genes causes production of SGCs.2.SGCs were detected in all epidermis with stomata distribution in asc octuple plants,which indicated that the promotion of GMC division by ACC is not tissue-specific.3.Block of ethylene synthesis or signaling failed to induce the formation of SGC.which demonstrate that ACC,but not ethylene,is required for the terminal division of GMCs.4.ACC fails to induce extra divisions of GMCs in wild type Arabidopsis,but causes extra divisions of GMCs n fama-1 and flp-lmyb88 mutants,which indicate that FAMA and FLP/MYB88 antagonize the positive role of ACC in controlling the division of GMCs.5.ACC promotes the expression of CDKB1 and CYCA2.In addition,ACC has no effect on the division of GMCs in cdkb1；11;2 and cyca2;234 mutants.Based on these results,we present a working model for ACC-mediated GMC division.In this model,ACC is crucial for the symmetric division of GMCs into GCs.ACC positively and FAMA/FLP/MYB88 negatively regulate the expression of CDKB1;1 and CYCA2;3 which are responsible for the division of GMCs.Under normal conditions(Figure 8A),ACC and FAMA/FLP/MYB88 maintain the appropriate expression of CDKB1;1 and CYCA2;3 in the GMCs and ensure the symmetric division of GMCs into GCs.When ACC synthesis is inhibited(Figure 8B),the expression of CDK1;1 and CYCA2;3 is downregulated,which disrupts the symmetric division of GMCs and then leads to the formation of SGCs.