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The Mg-chelatase H subunit is an abscisic acid receptor


Abscisic acid (ABA) is a vital phytohormone that regulates mainly stomatal aperture and seed development, but ABA receptors involved in these processes have yet to be determined. We previously identified from broad bean an ABA-binding protein (ABAR) potentially involved in stomatal signalling, the gene for which encodes the H subunit of Mg-chelatase (CHLH), which is a key component in both chlorophyll biosynthesis and plastid-to-nucleus signalling. Here we show that Arabidopsis ABAR/CHLH specifically binds ABA, and mediates ABA signalling as a positive regulator in seed germination, post-germination growth and stomatal movement, showing that ABAR/CHLH is an ABA receptor. We show also that ABAR/CHLH is a ubiquitous protein expressed in both green and non-green tissues, indicating that it might be able to perceive the ABA signal at the whole-plant level.

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Figure 1: ABAR binds ABA.
Figure 2: Changes in ABAR expression alter plant sensitivity to ABA.
Figure 3: ABAR-mediated ABA signalling is a distinct process.
Figure 4: Spatial expression of ABAR and alteration of ABA-signalling genes in transgenic plants.


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We thank N. H. Chua for the CLX inducible RNAi system, and Z. Z. Gong and X. C. Wang for advice and help on materials. This work was funded by the National Key Basic Research ‘973’ Program of China and National Natural Science Foundation of China (to D.P.Z.).

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Correspondence to Da-Peng Zhang.

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The sequence of the cDNA encoding part of CHLH is deposited in GenBank under accession number DQ376081. Reprints and permissions information is available at The authors declare no competing financial interests.

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This file contains Supplementary Methods, Supplementary Tables 1 and 2 and Supplementary Figures 1–9 (DOC 2980 kb)

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Shen, YY., Wang, XF., Wu, FQ. et al. The Mg-chelatase H subunit is an abscisic acid receptor. Nature 443, 823–826 (2006).

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