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Plant Molecular Biology

, Volume 80, Issue 4–5, pp 519–537

First Online: 27 September 2012Received: 18 May 2012Accepted: 26 August 2012

Abstract

The H subunit of Mg-chelatase CHLH was shown to regulate abscisic acid ABA signaling and the I subunit CHLI was also reported to modulate ABA signaling in guard cells. However, it remains essentially unknown whether and how the Mg-chelatase-catalyzed Mg-protoporphyrin IX-production differs from ABA signaling. Using a newly-developed surface plasmon resonance system, we showed that ABA binds to CHLH, but not to the other Mg-chelatase components-subunits CHLI, CHLD D subunit and GUN4. A new rtl1 mutant allele of the CHLH gene in Arabidopsis thaliana showed ABA-insensitive phenotypes in both stomatal movement and seed germination. Upregulation of CHLI1 resulted in ABA hypersensitivity in seed germination, while downregulation of CHLI conferred ABA insensitivity in stomatal response in Arabidopsis. We showed that CHLH and CHLI, but not CHLD, regulate stomatal sensitivity to ABA in tobacco Nicotiana benthamiana. The overexpression lines of the CHLD gene showed wild-type ABA sensitivity in Arabidopsis. Both the GUN4-RNA interference and overexpression lines of Arabidopsis showed wild-type phenotypes in the major ABA responses. These findings provide clear evidence that the Mg-chelatase-catalyzed Mg-ProtoIX production is distinct from ABA signaling, giving information to understand the mechanism by which the two cellular processes differs at the molecular level.

KeywordsH subunit of Mg-chelatase I subunit of Mg-chelatase D subunit of Mg-chelatase GUN4 ABA binding ABA signal transduction Accession numbersSequence data from this article can be found in the Arabidopsis Genome Initiative database under the following accession numbers: At5g13630 CHLH-ABAR, At4g18480 CHLI1, At5g45930 CHLI2, At1g08520 CHLD, and At3g59400 GUN4. Germplasm identification numbers: abi4-1, CS8104; abi5-1, CS8105; cch, CS6499; ch1-3, CS3121.

Shu-Yuan Du, Xiao-Feng Zhang and Zekuan Lu contributed equally to this work.

Electronic supplementary materialThe online version of this article doi:10.1007-s11103-012-9965-3 contains supplementary material, which is available to authorized users.

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Autor: Shu-Yuan Du - Xiao-Feng Zhang - Zekuan Lu - Qi Xin - Zhen Wu - Tao Jiang - Yan Lu - Xiao-Fang Wang - Da-Peng Zhang

Fuente: https://link.springer.com/



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