title: RopGEF7 regulates PLETHORA-dependent maintenance of the root stem cell niche in Arabidopsis.
abstract: The root stem cell niche defines the area that specifies and maintains the stem cells and is essential for the maintenance of root growth. Here, we characterize and examine the functional role of a quiescent center (QC)-expressed RAC/ROP GTPase activator, RopGEF7, in Arabidopsis thaliana. We show that RopGEF7 interacts with At RAC1 and overexpression of a C-terminally truncated constitutively active RopGEF7 (RopGEF7ΔC) activates RAC/ROP GTPases. Knockdown of RopGEF7 by RNA interference causes defects in embryo patterning and maintenance of the QC and leads to postembryonic loss of root stem cell population. Gene expression studies indicate that RopGEF7 is required for root meristem maintenance as it regulates the expression of PLETHORA1 (PLT1) and PLT2, which are key transcription factors that mediate the patterning of the root stem cell niche. Genetic analyses show that RopGEF7 interacts with PLT genes to regulate QC maintenance. Moreover, RopGEF7 is induced transcriptionally by auxin while its function is required for the expression of the auxin efflux protein PIN1 and maintenance of normal auxin maxima in embryos and seedling roots. These results suggest that RopGEF7 may integrate auxin-derived positional information in a feed-forward mechanism, regulating PLT transcription factors and thereby controlling the maintenance of root stem cell niches.
authors.affiliation: Key Laboratory of Ministry of Education for Rice Fertility Development and Stress Resistance, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Huili
authors.initials: H
authors.lastname: Liu
authors.forename: Jixiang
authors.initials: J
authors.lastname: Kong
authors.forename: Yali
authors.initials: Y
authors.lastname: Yang
authors.forename: Naichao
authors.initials: N
authors.lastname: Zhang
authors.forename: Ruijing
authors.initials: R
authors.lastname: Li
authors.forename: Jianbin
authors.initials: J
authors.lastname: Yue
authors.forename: Jiaqing
authors.initials: J
authors.lastname: Huang
authors.forename: Chuanyou
authors.initials: C
authors.lastname: Li
authors.forename: Alice Y
authors.initials: AY
authors.lastname: Cheung
authors.forename: Li-Zhen
authors.initials: LZ
authors.lastname: Tao
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000196:embryology* / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000494:pharmacology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000187:drug effects / Q000196:embryology / Q000235:genetics / Q000502:physiology; D009154:Mutation; D018517:Plant Roots / Q000187:drug effects / Q000196:embryology / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D018749:RNA, Plant / Q000235:genetics; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000187:drug effects / Q000196:embryology / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D055153:Stem Cell Niche / Q000502:physiology*; D013234:Stem Cells / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; C493246:PLT1 protein, Arabidopsis; C493247:PLT2 protein, Arabidopsis; C489522:RAC1 protein, Arabidopsis; D018749:RNA, Plant; D011993:Recombinant Fusion Proteins; C576218:RopGEF7 protein, Arabidopsis; D014157:Transcription Factors