In multicellular organisms,the balance be-tween cell division and differentiation determines organ size,and represents a central unknown in devel-opmental biology.In Arabidopsis roots,this balance is mediated between ...In multicellular organisms,the balance be-tween cell division and differentiation determines organ size,and represents a central unknown in devel-opmental biology.In Arabidopsis roots,this balance is mediated between cytokinin and auxin through a reg-ulatory circuit converging on the IAA3/SHORT HYPO-COTYL 2(SHY2)gene.Here,we show that crosstalk between brassinosteroids(BRs)and auxin occurs in the vascular transition zone to promote root meristem de-velopment.We found that BR increases root meristem size by up-regulating expression of the PINFORMED 7(PIN7)gene and down-regulating expression of the SHY2 gene.In addition,BES1 could directly bind to the pro-moter regions of both PIN7 and SHY2,indicating that PIN7 and SHY2 mediate the BR-induced growth of the root meristem by serving as direct targets of BES1.Moreover,the PIN7 overexpression and loss-of-function SHY2 mutant were sensitive to the effects of BR and could partially suppress the short-root phenotypes associated with deficient BR signaling.Interestingly,BRs could inhibit the accumulation of SHY2 protein in response to cytokinin.Taken together,these findings suggest that a complex equilibrium model exists in which regulatory interactions among BRs,auxin,and cytokinin regulate optimal root growth.展开更多
基金The work was supported by the National Natural ScienceFoundation of China(31670235)the Development Projectof Transgenic Crops of China(2016ZX08009-003-002)+2 种基金the National Natural Science Foundation of China(31970263 and 31972258)Fundamental Research Fundsfor the Central Universities(SCU2019D013)Applied basicproject of Sichuan Science and Technology Department(2018JY0192).
文摘In multicellular organisms,the balance be-tween cell division and differentiation determines organ size,and represents a central unknown in devel-opmental biology.In Arabidopsis roots,this balance is mediated between cytokinin and auxin through a reg-ulatory circuit converging on the IAA3/SHORT HYPO-COTYL 2(SHY2)gene.Here,we show that crosstalk between brassinosteroids(BRs)and auxin occurs in the vascular transition zone to promote root meristem de-velopment.We found that BR increases root meristem size by up-regulating expression of the PINFORMED 7(PIN7)gene and down-regulating expression of the SHY2 gene.In addition,BES1 could directly bind to the pro-moter regions of both PIN7 and SHY2,indicating that PIN7 and SHY2 mediate the BR-induced growth of the root meristem by serving as direct targets of BES1.Moreover,the PIN7 overexpression and loss-of-function SHY2 mutant were sensitive to the effects of BR and could partially suppress the short-root phenotypes associated with deficient BR signaling.Interestingly,BRs could inhibit the accumulation of SHY2 protein in response to cytokinin.Taken together,these findings suggest that a complex equilibrium model exists in which regulatory interactions among BRs,auxin,and cytokinin regulate optimal root growth.
