title: An essential protein that interacts with endosomes and promotes movement of the SHORT-ROOT transcription factor.
abstract: Plant cells can communicate through the direct transport of transcription factors [1-7]. One of the best-studied examples of this phenomenon is SHORT-ROOT (SHR), which moves from the stele cells into the endodermis and root tip of Arabidopsis, where it specifies endodermal cell identity and stem cell function, respectively [8-10]. In the endodermis, SHR upregulates the transcription factors SCARECROW (SCR) [2] and JACKDAW (JKD), which in turn inhibit movement of SHR from the endodermis [11]. Although much is known about the regulatory pathways that mediate expression and activity of SHR [1, 8-14], little is known about the factors that promote its movement or the movement of other transcription factors. We have identified a novel protein, SHORT-ROOT INTERACTING EMBRYONIC LETHAL (SIEL), that interacts with SHR, CAPRICE (CPC), TARGET OF MONOPTEROUS 7 (TMO7), and AGAMOUS-LIKE 21 (AGL21). Null alleles of SIEL are embryonic lethal. Hypomorphic alleles produce defects in root patterning and reduce SHR movement. Surprisingly, both SHR and SCR regulate expression of SIEL, so that siel/scr and siel/shr double mutants have extremely disorganized roots. SIEL localizes to the nucleus and cytoplasm of root cells where it is associated with endosomes. We propose that SIEL is an endosome-associated protein that promotes intercellular movement.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Koji
authors.initials: K
authors.lastname: Koizumi
authors.forename: Shuang
authors.initials: S
authors.lastname: Wu
authors.forename: Aurora
authors.initials: A
authors.lastname: MacRae-Crerar
authors.forename: Kimberly L
authors.initials: KL
authors.lastname: Gallagher
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000032:analysis; D016297:Mutagenesis, Site-Directed; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D014157:Transcription Factors / Q000032:analysis / Q000378:metabolism / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C410510:SHORT ROOT protein, Arabidopsis; C569695:Short-Root Interacting Embryonic Lethal protein, Arabidopsis; D014157:Transcription Factors; D049452:Green Fluorescent Proteins