Auxin-callose-mediated plasmodesmal gating is essential for tropic auxin gradient formation and signaling.
In plants, auxin functions as a master controller of development, pattern formation, morphogenesis, and tropic responses. A sophisticated transport system has evolved to allow the establishment of precise spatiotemporal auxin gradients that regulate specific developmental programs. A critical unresolved question relates to how these gradients can be maintained in the presence of open plasmodesmata that allow for symplasmic exchange of essential nutrients and signaling macromolecules. Here we addressed this conundrum using genetic, physiological, and cell biological approaches and identified the operation of an auxin-GSL8 feedback circuit that regulates the level of plasmodesmal-localized callose in order to locally downregulate symplasmic permeability during hypocotyl tropic response. This system likely involves a plasmodesmal switch that would prevent the dissipation of a forming gradient by auxin diffusion through the symplasm. This regulatory system may represent a mechanism by which auxin could also regulate symplasmic delivery of a wide range of signaling agents.
Brain Korea 21 Plus/World Class University Program, Division of Applied Life Science, Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea.
Xiao
X
Han
Brain Korea 21 Plus/World Class University Program, Division of Applied Life Science, Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea.
Tae Kyung
TK
Hyun
Brain Korea 21 Plus/World Class University Program, Division of Applied Life Science, Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea.
Minhua
M
Zhang
Brain Korea 21 Plus/World Class University Program, Division of Applied Life Science, Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea.
Ritesh
R
Kumar
Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA.
Eun-ji
EJ
Koh
Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA; Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL 32611, USA.
Byung-Ho
BH
Kang
Department of Plant Biology, College of Biological Sciences, University of California, Davis, Davis, CA 95616, USA. Electronic address: wjlucas@ucdavis.edu.
William J
WJ
Lucas
Brain Korea 21 Plus/World Class University Program, Division of Applied Life Science, Plant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea. Electronic address: kimjy@gnu.ac.kr.
Jae-Yean
JY
Kim
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D025461:Feedback, Physiological; D005936:Glucans / Q000378:metabolism*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D031425:Plasmodesmata / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D005936:Glucans; D007210:Indoleacetic Acids; C048306:callose; D005964:Glucosyltransferases; C549616:chorus protein, Arabidopsis