The TMK subfamily of receptor-like kinases in Arabidopsis display an essential role in growth and a reduced sensitivity to auxin

• Published in: PloS one 2013-04, Vol.8 (4), p.e60990
• Main Authors: Dai, Ning, Wang, Wuyi, Patterson, Sara E, Bleecker, Anthony B
• Format: Article
• Language: English
• Subjects: Arabidopsis; Arabidopsis - drug effects; Arabidopsis - enzymology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; auxins; BASIC BIOLOGICAL SCIENCES; Biology; cell cycle and cell division; Cell division; Cell growth; Cell proliferation; Chemistry; ENVIRONMENTAL SCIENCES; Expansion; Gene expression; Gene Expression Regulation, Plant - drug effects; Gene Expression Regulation, Plant - genetics; Genetic aspects; Glycine max; Growth; hypocotyl; Hypocotyls; Indoleacetic Acids - pharmacology; Insulin-like growth factors; Kinases; Laboratories; Leaves; Leucine; Ligands; Mutants; Mutation; Organs; phenotypes; Phosphotransferases; Plant growth; Plant sciences; Plants, Genetically Modified - drug effects; Plants, Genetically Modified - enzymology; Plants, Genetically Modified - genetics; Proteins; seedings; Sensitivity; Signaling
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0060990

Mechanisms that govern the size of plant organs are not well understood but believed to involve both sensing and signaling at the cellular level. We have isolated loss-of-function mutations in the four genes comprising the transmembrane kinase TMK subfamily of receptor-like kinases (RLKs) in Arabidopsis. These TMKs have an extracellular leucine-rich-repeat motif, a single transmembrane region, and a cytoplasmic kinase domain. While single mutants do not display discernable phenotypes, unique double and triple mutant combinations result in a severe reduction in organ size and a substantial retardation in growth. The quadruple mutant displays even greater severity of all phenotypes and is infertile. The kinematic studies of root, hypocotyl, and stamen filament growth reveal that the TMKs specifically control cell expansion. In leaves, TMKs control both cell expansion and cell proliferation. In addition, in the tmk double mutants, roots and hypocotyls show reduced sensitivity to applied auxin, lateral root induction and activation of the auxin response reporter DR5: GUS. Thus, taken together with the structural and biochemical evidence, TMKs appear to orchestrate plant growth by regulation of both cell expansion and cell proliferation, and as a component of auxin signaling.