Molecular Plant Advance Access originally published online on May 19, 2009
Molecular Plant 2009 2(4):688-699; doi:10.1093/mp/ssp026
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A Truncated Arabidopsis NUCLEOSOME ASSEMBLY PROTEIN 1, AtNAP1;3T, Alters Plant Growth Responses to Abscisic Acid and Salt in the Atnap1;3-2 Mutant
a Institut de Biologie Moléculaire des Plantes (IBMP) du CNRS, Université de Strasbourg (UdS), 12 rue du Général Zimmer, 67084 Strasbourg Cédex, France
b State Key Laboratory of Genetic Engineering, Institute of Plant Biology, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai 200433, People's Republic of China
1 To whom correspondence should be addressed. E-mail aiwudong{at}fudan.edu.cn, fax +86 21 65 64 36 03.
2 To whom correspondence should be addressed. E-mail Wen-Hui.Shen{at}ibmp-ulp.u-strasbg.fr, fax +33 3 88 61 44 42.
Chromatin remodeling is thought to have crucial roles in plant adaptive response to environmental stimulus. Here, we report that, in Arabidopsis, the evolutionarily conserved histone chaperone, NUCLEOSOME ASSEMBLY PROTEIN 1 (NAP1), is involved in plant response to abscisic acid (ABA), a phytohormone important in stress adaptation. We show that simultaneous loss-of-function of AtNAP1;1, AtNAP1;2, and AtNAP1;3 (the triple mutant m123-1) caused a slight hypersensitive response to ABA in seedling growth. Strikingly, the other triple mutant m123-2 containing a different mutant allele of AtNAP1;3, the Atnap1;3-2 allele, showed a hyposensitive response to ABA and a decreased tolerance to salt stress. This ABA-hyposensitive and salt response phenotype specifically associated with the Atnap1;3-2 mutant allele. We show that this mutant allele produced a truncated protein, AtNAP1;3T, which lacks 34 amino acids at the C-terminus compared to the wild-type protein AtNAP1;3. We further show that the heterozygous plants containing the Atnap1;3-2 mutant allele as well as transgenic plants overexpressing AtNAP1;3T exhibit ABA-hyposensitive phenotype. It thus indicates that AtNAP1;3T functions as a dominant negative factor in ABA response. The expression of some ABA-responsive genes, including genes encoding protein kinases and transcription regulators, was found perturbed in the mutant and in the AtNAP1;3T transgenic plants. Taken together, our study uncovered AtNAP1 proteins as positive regulators and AtNAP1;3T as a negative regulator in ABA signaling pathways, providing a novel link of chromatin remodeling to hormonal and stress responses.
Key Words: Histone chaperone • chromatin • epigenetics • abiotic stress • Arabidopsis