Analysis Of Hypocotyl Phenotype Of BASL Mutant And Its Response To Hormones

BASL is a protein which is required for the development and patterning of stomata in plant epidermis.Its function in stomata development has been investigated deeply,while little is known about its function in other developmental background and how it is regulated.In this paper,two basl mutants,basl-1 and basl-2,are used to detect other development defects to decipher the function of BASL,and promoter-drived GUS(pBASL:GUS)was used as marker gene to detect itspromoter activity under different growth conditions and with or without treatment of exogenous hormones.The main results are as follows:1.Hypocotyl length and response to hormones of basl-1 is different from that of wild type and basl-2 seedlings.Seedlings of basl-1 has hypocotyl longer than that of wild type and basl-2 when growing under light,and basl-1 seedlings is less sensitive to 2,4-D(synthesis auxin)and has less phototropic bending of hypocotyl compared with wild type and basl-2.2.The cause of long hypocotyl in basl-1 seedlings wasinvestigated and the results showed that:A,The cell number of hypocotyl was not changed in basl-1,but the length of hypocotyl cells increased.B,The middle region of hypocotyl in basl-1 seedlings kept elongation while those of wt and basl-2 cease at some time point.The long hypocotyl of basl-1 seedlings resulted in theconstantly elongation of cells located in the middle of hypocotyl,whose elongation should be inhibitedunder the light growth condition as in wild type and basl-2.This result indicated that BASL protein may function in the inhibitionof cellelongation of hypocotyl under light.C,The morphology of hypocotyl cells didnot change in basl-1 seedlings.3.Seedling of basl-1 is less sensitive to 2,4-D which can induce callus formation of wild type and basl-2.In wild type,exogenous 2,4-D can effectively inhibite the elongation of hypocotyl and root,induce the dedifferentiation of these cells,and callus formation after their division and expansion.while in basl-1,the expanding and shorten of hypocotyl and root are inhibited contrasted to wild type and basl-2 seedlings.This indicates that the division of differentiated cells and formation of callus induced by 2,4-D need normal BASL protein function.4.Seedlings of basl-1 have less bending hypocotyl compared with wt and basl-2 under light growth condition.The phototropicbending of hypocotyl could be mimiced by exogenous IAA in wt and whilebasl-1 seedlings showed insensitive to IAA.5.The inhibition of hypocotyl elongation of Arabidopsis thaliana seedlings by light was affected by many kinds of hormones.Seedlings ofbasl-1exibited resistance to IAA,BFA,NOA and Bikinin treatment,while they were sensitive to exogenous NPA,ZT and ACC compared with wt.6.BASL promoter is active in both light and dark.Expression of BASL is regulated by auxin.Acitivity of BASL promoterin hypocotyl and vasculature are strengthened by IAA treatment and dampened by PEO-IAA(a blocker of auxin signaling)treatment.7.Expression of BASL is aslo regulated by other hormones.Activity of BASL promoterin hypocotyl vasculature was elevated by exogenous treatment of BR,ABA and ZT,while it was inhibited by Bikinin and GA3.Expression of ABSL in root vasculature was elevated by exogenous treatment of BR,GA3 and MeJA,while it is inhibited by Bikinin,ZT and ACC.Expression of BASL in cotyledon epidermis was elevated by exogenous treatment of ABA,ZT,MeJA and ACC,while inhibited by BR.Theseresults indicated that a variety of hormones involved in expressionregulation of BASL.These results proved that BASL functions not only in polarity and cell fate determination in stomata development,but also in other development processes such as hypocotyl elongation and phototropic response.And the expression of BASL in difference organs was regulated by hormones.This work laid good foundation for further research on the function of BASL.