Auxin influx carriers control vascular patterning and xylem differentiation in Arabidopsis thaliana.
Auxin is an essential hormone for plant growth and development. Auxin influx carriers AUX1/LAX transport auxin into the cell, while auxin efflux carriers PIN pump it out of the cell. It is well established that efflux carriers play an important role in the shoot vascular patterning, yet the contribution of influx carriers to the shoot vasculature remains unknown. Here, we combined theoretical and experimental approaches to decipher the role of auxin influx carriers in the patterning and differentiation of vascular tissues in the Arabidopsis inflorescence stem. Our theoretical analysis predicts that influx carriers facilitate periodic patterning and modulate the periodicity of auxin maxima. In agreement, we observed fewer and more spaced vascular bundles in quadruple mutants plants of the auxin influx carriers aux1lax1lax2lax3. Furthermore, we show AUX1/LAX carriers promote xylem differentiation in both the shoot and the root tissues. Influx carriers increase cytoplasmic auxin signaling, and thereby differentiation. In addition to this cytoplasmic role of auxin, our computational simulations propose a role for extracellular auxin as an inhibitor of xylem differentiation. Altogether, our study shows that auxin influx carriers AUX1/LAX regulate vascular patterning and differentiation in plants.
Department of Molecular Genetics, Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Barcelona, Spain.
Norma
N
Fàbregas
Department of Structure and Constituents of Matter, Faculty of Physics, University of Barcelona, Barcelona, Spain.
Pau
P
Formosa-Jordan
Department of Molecular Genetics, Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Barcelona, Spain.
Ana
A
Confraria
Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Department of Biosciences, University of Helsinki, Helsinki, Finland.
Riccardo
R
Siligato
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, North Carolina, United States of America.
Jose M
JM
Alonso
School of Biosciences and Centre for Plant Integrative Biology, University of Nottingham, Nottingham, United Kingdom.
Ranjan
R
Swarup
School of Biosciences and Centre for Plant Integrative Biology, University of Nottingham, Nottingham, United Kingdom.
Malcolm J
MJ
Bennett
Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Department of Biosciences, University of Helsinki, Helsinki, Finland.
Ari Pekka
AP
Mähönen
Department of Molecular Genetics, Centre for Research in Agricultural Genomics (CRAG) CSIC-IRTA-UAB-UB, Barcelona, Spain.
Ana I
AI
Caño-Delgado
Department of Structure and Constituents of Matter, Faculty of Physics, University of Barcelona, Barcelona, Spain.
Marta
M
Ibañes
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D063245:Plant Development / Q000235:genetics; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development; D052584:Xylem / Q000235:genetics* / Q000254:growth & development
C100794:AUX1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; C578308:LAX1 protein, Arabidopsis; C578309:LAX2 protein, Arabidopsis; C531125:LAX3 protein, Arabidopsis; D026901:Membrane Transport Proteins