Analysis Of The Different Sensitivity With The Stomatal Development Responding To Hormone In Different Basl Mutants

Stomata are epidermis valves responsible for gas exchange between plants and the environment.Stomatal development is regulated by internal and external environmental factors.BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE?BASL?protein is one of the main regulators of stomatal lineage precursor cell asymmetric division.Hormones also participate in the regulation of multiple cellular processes including asymmetric cell division.Taking different mutants of BASL as subjects,responses of stomatal development of different basl alleles to exogenous hormones were studied and the interaction of BASL with hormones was discussed.The main results are as follows:?1?Different hormones affect different stages during stomatal development on the epidermis in Arabidopsis.On the abaxial epidermis of cotyledon in wild type Arabidopsis Col?gl1?,exogenous 2,4-D and NOA treatment increase the asymmetric division of SLGC.The asymmetric cell divisions of the stomatal precursor were turned into symmetric divisions by NPA treatment,and stomatal clusters formed owing to the development of both daughter cells into stoma.GA₃ promotes the asymmetric divisions of stomatal precursor cells while inhibits the late stages of differentiation and maturation.On the contrary,as GA biosynthesis inhibitor,PAC promotes the late stages of stomatal development.Me JA treatment promotes the expansion and differentiation of PV cells,while SA promotes the division of epidermal cells but inhibits the proliferation and differentiation of PV cells.ACC treatment enhance the asymmetric cell division of stomatal lineages including SLGC and the symmetric cell division of PV cells,and inhibits the proliferation and differentiation of PV cells.AOA is in the process of symmetric division of cells.?2?The responses of null mutant basl-2 mutant to exogenous hormones as for stomatal development on the abaxial cotyledon epidermis are as follows: Stomatal development of basl-2 is not sensitive to GA₃ treatment,but do response to other hormone more or less.The insensitivity of basl-2 to GA₃ indicated that GA may require the BASL protein function to improve the early stage of stomatal development.In addition,treatment with NPA,an inhibitor of auxin polar transport,to block auxin outward flowing resulted in the transition of asymmetric cell divisions into symmetric cell divisions in the stomatal precursors,leading to the same defect and stomatal clusters as in basl-2 mutant background.This result hints that the polar auxin transport especially the export of auxin from the precursor cells plays a vital role in their asymmetric division as BASL.?3?Four alleles of basl response differently to exogenous hormone treatments as for the stomatal development on the abaxial epidermis of cotyledon.basl-1,basl-4c and basl-6c responded to hormones with great similarity,but basl-2 responded differently with exogenous hormone treatments.Exogenous Me JA treated with basl-2 mutants,forming the larger stomatal clusters.basl-2 showed a stronger sensitivity to the response of ACC and AOA.In addition,the basl-1 mutant exhibited more resistant to the treatment of 2,4-D and NOA than the other three.This might be owing to the truncated BASL protein produced in this background.Moreover,basl-1 is very sensitive to GA₃ and blocking of GA synthesis,PAC,can also be shown that the promotion effect of GA mediated BASL may also be regulated by the BASL protein structure.?4?Responses of stomatal development on the epidermis of hypocotyl to hormones are as follows: Exogenous NOA,ACC and AOA promotes the cell division at the early stage of stomatal development and increase the number of stomata.2,4-D promotes cell division in hypocotyl and induces the formation of callus.NPA inhibits stomatal formation on the hypocotyl epidermis.GA₃ maybe cannot influence the stomata while PAC completely diminishes the formation of stomata on the epidermis of hypocotyl.It is indicated that the biosynthesis of GAs is necessary for epidermis cells of hypocotyl to enter the stomatal development pathway under any nutritional conditions.Both Me JA and SA inhibits stomatal formation on hypocotyl epidermis,and exogenous Me JA can induce the stomatal cluster.?5?Response of basl-2 mutant to exogenous hormones as for the hypocotyl stomatal development are as follows: null mutant basl-2 has the same response to exogenous IAA,2,4-D,NOA,GA₃,PAC,Me JA,SA,ACC and AOA as the wild type col?gl1?,which indicates that BASL is not needed for these hormones to regulate the stomatal development on hypocotyl epidermis.?6?Four alleles of basl response differently to exogenous hormone treatments as for the stomatal development on the hypocotyl epidermis.Four mutants responds to exogenous Me JA,SA,GA₃,and PAC with great similarity but basl-1 differ in the response to 2,4-D,NOA and ACC.basl-1 mutant showed higher resistance to 2,4-D and NOA induced callus formation,and insensitive to ACC and AOA induced division promotion than the other three genetic backgrounds.In conclusion,this study revealed that multiple hormones participate in the regulation of asymmetric cell division of precursors during early stages of stomatal development.But different hormones have their own unique and separated targets and there is crosstalk between hormones.GA may need BASL to regulate the asymmetric cell division.In addition,the difference response to hormones between cotyledon and hypocotyl reflects the organ specificity and complexity of stomatal development regulation.In addition,the different responses of basl mutants to hormones indicated that different domain of BASL protein might function in hormones sensing and downstream responses.