Functional characterization of the CKRC1/TAA1 gene and dissection of hormonal actions in the Arabidopsis root.
Cytokinin (CK) influences many aspects of plant growth and development, and its function often involves intricate interactions with other phytohormones such as auxin and ethylene. However, the molecular mechanisms underlying the role of CK and its interactions with other growth regulators are still poorly understood. Here we describe the isolation and characterization of the Arabidopsis CK-induced root curling 1 (ckrc1) mutant. CKRC1 encodes a previously identified tryptophan aminotransferase (TAA1) involved in the indole-3-pyruvic acid (IPA) pathway of indole-3-acetic acid (IAA) biosynthesis. The ckrc1 mutant exhibits a defective root gravitropic response (GR) and an increased resistance to CK in primary root growth. These defects can be rescued by exogenous auxin or IPA. Furthermore, we show that CK up-regulates CKRC1/TAA1 expression but inhibits polar auxin transport in roots in an AHK3/ARR1/12-dependent and ethylene-independent manner. Our results suggest that CK regulates root growth and development not only by down-regulating polar auxin transport, but also by stimulating local auxin biosynthesis.
Institute of Cell Biology, School of Life Sciences, Lanzhou University, Lanzhou 73000, China.
Zhao-Yang
ZY
Zhou
Chun-Guang
CG
Zhang
Lei
L
Wu
Cai-Guo
CG
Zhang
Juan
J
Chai
Ming
M
Wang
Ajay
A
Jha
Peng-Fei
PF
Jia
Su-Juan
SJ
Cui
Ming
M
Yang
Rujin
R
Chen
Guang-Qin
GQ
Guo
D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001593:Benzyl Compounds; D001692:Biological Transport; D003001:Cloning, Molecular; D003583:Cytokinins / Q000378:metabolism* / Q000494:pharmacology; D005030:Ethylenes / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D018522:Gravitropism; D018546:Hypocotyl / Q000187:drug effects / Q000254:growth & development; D007210:Indoleacetic Acids / Q000378:metabolism* / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007701:Kinetin / Q000494:pharmacology; D009154:Mutation; D010671:Phenylurea Compounds / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011687:Purines; D013830:Thiadiazoles / Q000494:pharmacology; D051279:Tryptophan Transaminase / Q000378:metabolism*
D029681:Arabidopsis Proteins; D001593:Benzyl Compounds; D003583:Cytokinins; D005030:Ethylenes; D007210:Indoleacetic Acids; D007211:Indoles; D010671:Phenylurea Compounds; D010937:Plant Growth Regulators; D011687:Purines; D013830:Thiadiazoles; C016785:thidiazuron; C008122:indol-3-yl pyruvic acid; C036216:ethylene; D051279:Tryptophan Transaminase; C480551:benzylaminopurine; D007701:Kinetin