Tsai, Yu-Chang , Delk, Nikki , Chowdhury, Naweed , Braam, Janet .
Arabidopsis Calcium Sensors Regulate Transition to Flowering and Nitric Oxide Accumulation.
Ca2+-binding proteins encoded in the Arabidopsis genome are predicted to mediate cellular responses to Ca2+ fluctuations. In the present work, we find two related putative Ca2+ sensors, CML23 and CML24, regulate the transition to flowering. The cml24-4 allele behaves as a loss of function and causes late flowering specifically under long days, indicating the CML24 is required for proper functioning of the photoperiod pathway. Conversely, cml24-2, with a substitution of a conserved amino acid in an EF-hand Ca2+-binding motif, flowers early. Opposing phenotypes suggest that CML24 can act as a switch in the photoperiod pathway regulating flowering transition. Based on quantitative RT-PCR, we place CML24 function upstream of Constans (CO). cml24-4 has reduced CO expression; cml24-2 has elevated CO expression. Mutants harboring loss of function alleles of both CML24 and the closely related paralog, CML23, are also defective in the autonomous pathway regulating flowering transition. cml23/cml24 double mutants have elevated Flowering Locus C (FLC) expression and flower late under all photoperiods. Both single and double mutants respond normally to gibberellin and vernalization. These roles for CML23 and CML24 in regulating flowering transition may link circadian- and light-regulated Ca2+ fluctuations to the control of flowering regulation. Nitric oxide (NO) also regulates CO and FLC expression and thus has been implicated in controlling the flowering transition. Through measurement of NO accumulation in the cml23 and cml24 mutants, we find that CML23/CML24 regulate NO levels, act upstream of NO synthase, and regulate flowering transition through NO accumulation.
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1 - Rice University, Biochemistry and Cell Biology, 6100 Main Street, Houston, TX, 77005, USA
2 - Rice University, Biochemistry and Cell Biology
Presentation Type: ASPB Minisymposium
Location: Continental A/Hilton
Date: Monday, July 9th, 2007
Time: 11:55 AM