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Wang Z.,China Agricultural University | Meng P.,China Agricultural University | Zhang X.,China Agricultural University | Ren D.,China Agricultural University | And 2 more authors.
Plant Journal | Year: 2011

The Arabidopsis copine gene BON1 encodes a calcium-dependent phospholipid-binding protein involved in plant growth homeostasis and disease resistance. However, the biochemical and molecular mechanisms by which BON1 modulates plant growth and defense responses are not well understood. Here, we show that BON1 interacts physically with the leucine-rich-repeat receptor-like kinases BIR1 (BAK1-interacting receptor-like kinase 1) and pathogen-associated molecular pattern (PAMP) receptor regulator BAK1 in vitro and in vivo. Additionally, bon1 and bir1 mutants exhibit synergistic interaction. While a bir1 null mutant has similar growth and cell-death defects compared with bon1, a bir1 bon1 double mutant displays more severe phenotypes than does the single mutants. The bon1-1 and bir1-1 phenotypes are partially suppressed by overexpression of BIR1 and BON1, respectively. Furthermore, the bir1 phenotype is attenuated by a loss-of-function mutation in the resistance (R) gene SNC1 (Suppressor of npr1-1, constitutive 1), which mediates defense responses in bon1. Intriguingly, BON1 and BIR1 can be phosphorylated by BAK1 in vitro. Our findings suggest that BIR1 functions as a negative regulator of plant resistance and that BON1 and BIR1 might modulate both PAMP- and R protein-triggered immune responses. © 2011 Blackwell Publishing Ltd.

Wang Y.,China Agricultural University | Zhang Y.,China Agricultural University | Wang Z.,China Agricultural University | Zhang X.,China Agricultural University | And 2 more authors.
Plant Journal | Year: 2013

Low temperature is an environmental factor that affects plant growth and development and plant-pathogen interactions. How temperature regulates plant defense responses is not well understood. In this study, we characterized chilling-sensitive mutant 1 (chs1), and functionally analyzed the role of the CHS1 gene in plant responses to chilling stress. The chs1 mutant displayed a chilling-sensitive phenotype, and also displayed defense-associated phenotypes, including extensive cell death, the accumulation of hydrogen peroxide and salicylic acid, and an increased expression of PR genes: these phenotypes indicated that the mutation in chs1 activates the defense responses under chilling stress. A map-based cloning analysis revealed that CHS1 encodes a TIR-NB-type protein. The chilling sensitivity of chs1 was fully rescued by pad4 and eds1, but not by ndr1. The overexpression of the TIR and NB domains can suppress the chs1-conferred phenotypes. Interestingly, the stability of the CHS1 protein was positively regulated by low temperatures independently of the 26S proteasome pathway. This study revealed the role of a TIR-NB-type gene in plant growth and cell death under chilling stress, and suggests that temperature modulates the stability of the TIR-NB protein in Arabidopsis. © 2013 John Wiley & Sons Ltd.

Shi Y.,China Agricultural University | Wang Z.,China Agricultural University | Meng P.,China Agricultural University | Tian S.,China Agricultural University | And 3 more authors.
New Phytologist | Year: 2013

ALTERED MERISTEM PROGRAM1 (AMP1) encodes a glutamate carboxypeptidase that plays an important role in shoot apical meristem development and phytohormone homeostasis. We isolated a new mutant allele of AMP1, amp1-20, from a screen for abscisic acid (ABA) hypersensitive mutants and characterized the function of AMP1 in plant stress responses. amp1 mutants displayed ABA hypersensitivity, while overexpression of AMP1 caused ABA insensitivity. Moreover, endogenous ABA concentration was increased in amp1-20- and decreased in AMP1-overexpressing plants under stress conditions. Application of ABA reduced the AMP1 protein level in plants. Interestingly, amp1 mutants accumulated excess superoxide and displayed hypersensitivity to oxidative stress. The hypersensitivity of amp1 to ABA and oxidative stress was partially rescued by reactive oxygen species (ROS) scavenging agent. Furthermore, amp1 was tolerant to freezing and drought stress. The ABA hypersensitivity and freezing tolerance of amp1 was dependent on ABA signaling. Moreover, amp1 had elevated soluble sugar content and showed hypersensitivity to high concentrations of sugar. By contrast, the contents of amino acids were changed in amp1 mutant compared to the wild-type. This study suggests that AMP1 modulates ABA, oxidative and abotic stress responses, and is involved in carbon and amino acid metabolism in Arabidopsis. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Bhadauria V.,China Agricultural University | Bhadauria V.,University of Saskatchewan | Wang L.-X.,China Agricultural University | Peng Y.-L.,China Agricultural University | Peng Y.-L.,National Plant Gene Research Center
Biology Direct | Year: 2010

Background: The rice blast disease caused by Magnaporthe oryzae is a major constraint on world rice production. The conidia produced by this fungal pathogen are the main source of disease dissemination. The morphology of conidia may be a critical factor in the spore dispersal and virulence of M. oryzae in the field. Deletion of a conidial morphology regulating gene encoding putative transcriptional regulator COM1 in M. oryzae resulted in aberrant conidial shape, reduced conidiation and attenuated virulence.Results: In this study, a two-dimensional gel electrophoresis/matrix assisted laser desorption ionization- time of flight mass spectrometry (2-DE/MALDI-TOF MS) based proteomics approach was employed to identify the cellular and molecular components regulated by the COM1 protein (COM1p) that might contribute to the aberrant phenotypes in M. oryzae. By comparing the conidial proteomes of COM1 deletion mutant and its isogenic wild-type strain P131, we identified a potpourri of 31 proteins that exhibited statistically significant alterations in their abundance levels. Of these differentially regulated proteins, the abundance levels of nine proteins were elevated and twelve were reduced in the Δcom1 mutant. Three proteins were detected only in the Δcom1 conidial proteome, whereas seven proteins were apparently undetectable. The data obtained in the study suggest that the COM1p plays a key role in transcriptional reprogramming of genes implicated in melanin biosynthesis, carbon and energy metabolism, structural organization of cell, lipid metabolism, amino acid metabolism, etc. Semi-quantitative RT-PCR analysis revealed the down-regulation of genes encoding enzymes involved in melanin biosynthesis in the COM1 mutant.Conclusions: Our results suggest that the COM1p may regulate the transcription of genes involved in various cellular processes indispensable for conidial development and appressorial penetration. These functions are likely to contribute to the effects of COM1p upon the aberrant phenotypes of M. oryzae.Reviewers: This article is reviewed by George V. Shpakovski, Karthikeyan Sivaraman (nominated by M. Madan Babu) and Lakshminarayan M. Iyer. © 2010 Bhadauria et al; licensee BioMed Central Ltd.

Yang H.,China Agricultural University | Shi Y.,China Agricultural University | Liu J.,China Agricultural University | Guo L.,China Agricultural University | And 3 more authors.
Plant Journal | Year: 2010

Low temperature is one of environmental factors that restrict plant growth homeostasis and plant-pathogen interactions. Recent studies suggest a link between temperature responses and defense responses; however, the underlying molecular mechanisms remain unclear. In this study, the chilling sensitive 3 (chs3-1) mutant in Arabidopsis was characterized. chs3-1 plants showed arrested growth and chlorosis when grown at 16°C or when shifted from 22 to 4°C. chs3-1 plants also exhibited constitutively activated defense responses at 16°C, which were alleviated at a higher temperature (22°C). Map-based cloning of CHS3 revealed that it encodes an unconventional disease resistance (R) protein belonging to the TIR-NB-LRR class with a zinc-binding LIM domain (Lin-11, Isl-1 and Mec-3 domains) at the carboxyl terminus. The chs3-1 mutation in the conserved LIM-containing domain led to the constitutive activation of the TIR-NB-LRR domain. Consistently, the growth and defense phenotypes of chs3-1 plants were completely suppressed by eds1, sgt1b and rar1, partially by pad4 and nahG, but not by npr1 and ndr1. Intriguingly, chs3-1 plants grown at 16°C showed enhanced tolerance to freezing temperatures. This tolerance was correlated with growth defect and cell death phenotypes caused by activated defense responses. Other mutants with activated defense responses, including cpr1, cpr5 and slh1 also displayed enhanced freezing tolerance. These findings revealed a role of an unconventional mutant R gene in plant growth, defense response and cold stress, suggesting a mutual interaction between cold signaling and defense responses. © 2010 Blackwell Publishing Ltd.

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