Arabidopsis cytokinin receptor mutants reveal functions in shoot growth, leaf senescence, seed size, germination, root development, and cytokinin metabolism.

Content Provider	Semantic Scholar
Author	Riefler, Michael Novák, Ondřej Strnad, Miroslav Schmülling, Thomas
Copyright Year	2006
Abstract	We used loss-of-function mutants to study three Arabidopsis thaliana sensor histidine kinases, AHK2, AHK3, and CRE1/AHK4, known to be cytokinin receptors. Mutant seeds had more rapid germination, reduced requirement for light, and decreased far-red light sensitivity, unraveling cytokinin functions in seed germination control. Triple mutant seeds were more than twice as large as wild-type seeds. Genetic analysis indicated a cytokinin-dependent endospermal and/or maternal control of embryo size. Unchanged red light sensitivity of mutant hypocotyl elongation suggests that previously reported modulation of red light signaling by A-type response regulators may not depend on cytokinin. Combined loss of AHK2 and AHK3 led to the most prominent changes during vegetative development. Leaves of ahk2 ahk3 mutants formed fewer cells, had reduced chlorophyll content, and lacked the cytokinin-dependent inhibition of dark-induced chlorophyll loss, indicating a prominent role of AHK2 and, particularly, AHK3 in the control of leaf development. ahk2 ahk3 double mutants developed a strongly enhanced root system through faster growth of the primary root and, more importantly, increased branching. This result supports a negative regulatory role for cytokinin in root growth regulation. Increased cytokinin content of receptor mutants indicates a homeostatic control of steady state cytokinin levels through signaling. Together, the analyses reveal partially redundant functions of the cytokinin receptors and prominent roles for the AHK2/AHK3 receptor combination in quantitative control of organ growth in plants, with opposite regulatory functions in roots and shoots.
Starting Page	40
Ending Page	54
Page Count	15
File Format	PDF HTM / HTML
DOI	10.1105/tpc.105.037796
PubMed reference number	16361392
Journal	Medline
Volume Number	18
Issue Number	1
Alternate Webpage(s)	http://www.plantcell.org/content/plantcell/early/2005/12/16/tpc.105.037796.full.pdf
Alternate Webpage(s)	http://www.plantcell.org/content/plantcell/18/1/40.full.pdf
Alternate Webpage(s)	http://hos.ufl.edu/kleeweb/classpapers/riefler%20et%20al%20plant%20cell.pdf
Alternate Webpage(s)	https://doi.org/10.1105/tpc.105.037796
Journal	The Plant cell
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article