The MEDIATOR genes MED12 and MED13 control Arabidopsis root system configuration influencing sugar and auxin responses
Arabidopsis med12 and med13 mutants exhibit shoot and root phenotypes related to an altered auxin homeostasis. Sucrose supplementation reactivates both cell division and elongation in primary roots as well as auxin-responsive and stem cell niche gene expression in these mutants. An analysis of primary root growth of WT, med12, aux1-7 and med12 aux1 single and double mutants in response to sucrose and/or N-1-naphthylphthalamic acid (NPA) placed MED12 upstream of auxin transport for the sugar modulation of root growth.
The MEDIATOR (MED) complex plays diverse functions in plant development, hormone signaling and biotic and abiotic stress tolerance through coordination of transcription. Here, we performed genetic, developmental, molecular and pharmacological analyses to characterize the role of MED12 and MED13 on the configuration of root architecture and its relationship with auxin and sugar responses. Arabidopsis med12 and med13 single mutants exhibit shoot and root phenotypes consistent with altered auxin homeostasis including altered primary root growth, lateral root development, and root hair elongation. MED12 and MED13 were required for activation of cell division and elongation in primary roots, as well as auxin-responsive and stem cell niche gene expression. Remarkably, most of these mutant phenotypes were rescued by supplying sucrose to the growth medium. The growth response of primary roots of WT, med12, aux1-7 and med12 aux1 single and double mutants to sucrose and application of auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) revealed the correlation of med12 phenotype with the activity of the auxin intake permease and suggests that MED12 acts upstream of AUX1 in the root growth response to sugar. These data provide compelling evidence that MEDIATOR links sugar sensing to auxin transport and distribution during root morphogenesis.
KeywordsArabidopsis thaliana Sugar Auxin Root development MEDIATOR complex
Cyclin dependent kinase
Green fluorescent protein
Lateral root primordia
Target of rapamycin
Yellow fluorescent protein
We are thankful to the Arabidopsis stock center for kindly providing us with Arabidopsis mutant seeds. Drs. Tom Guilfoyle, Ben Scheres, Philip N. Benfey, Stewart Gillmor and Alfredo Cruz Ramírez are thanked for providing us Arabidopsis mutant and transgenic lines. This work was supported by grants from the Consejo Nacional de Ciencia y Tecnología (CONACYT, México, Grant No. 177775), the Consejo de la Investigación Científica (UMSNH, México, Grant No. CIC 2.26), and the UNAM-DGAPA-PAPIIT (Grant IN207014 to AAGG and JSLB).
JLB, JRG, LFRH, JCPR conceived and performed experiments. JRG, JLB wrote the manuscript. AAG, JSLB conceived and performed experiments and provided feedback. JLB and AAG repeatedly applied for funding.
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