Difference between revisions of "Xa10"
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==Function== | ==Function== | ||
| − | [[File:xa10 | + | [[File:xa10 figure 2.png|right|thumb|150px|''figure 1 (from reference <ref name="ref1" />).'']] |
Bacterial blight of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), is the most devastating disease of rice (Oryza sativa L). Rice lines that carry resistance (R) gene Xa10 confer race-specific resistance to Xoo strains harboring avirulence (Avr) gene avrXa10. | Bacterial blight of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), is the most devastating disease of rice (Oryza sativa L). Rice lines that carry resistance (R) gene Xa10 confer race-specific resistance to Xoo strains harboring avirulence (Avr) gene avrXa10. | ||
The rice TAL effector-dependent resistance protein Xa10 trigger cell death and calcium depletion in the Endoplasmic Reticulum.Xa10 is a transcription activator-like (TAL) effector-dependent R gene for resistance to bacterial blight in rice (Oryza sativa). Xa10 contains a binding element for the TAL effector AvrXa10 (EBEAvrXa10) in its promoter(from reference <ref name="ref2" />), and AvrXa10 specifically induces Xa10 expression. Expression of Xa10 induces programmed cell death in rice, Nicotiana benthamiana, and mammalian HeLa cells. The Xa10 gene product Xa10 localizes as hexamers in the endoplasmic reticulum (ER) and is associated with ER Ca (2+) depletion in plant and HeLa cells. | The rice TAL effector-dependent resistance protein Xa10 trigger cell death and calcium depletion in the Endoplasmic Reticulum.Xa10 is a transcription activator-like (TAL) effector-dependent R gene for resistance to bacterial blight in rice (Oryza sativa). Xa10 contains a binding element for the TAL effector AvrXa10 (EBEAvrXa10) in its promoter(from reference <ref name="ref2" />), and AvrXa10 specifically induces Xa10 expression. Expression of Xa10 induces programmed cell death in rice, Nicotiana benthamiana, and mammalian HeLa cells. The Xa10 gene product Xa10 localizes as hexamers in the endoplasmic reticulum (ER) and is associated with ER Ca (2+) depletion in plant and HeLa cells. | ||
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The products of the TAL effector-dependent R genes show no apparent sequence similarities(from reference <ref name="ref4" />). | The products of the TAL effector-dependent R genes show no apparent sequence similarities(from reference <ref name="ref4" />). | ||
==Structure== | ==Structure== | ||
| − | [[File: | + | [[File:figure1.png|right|thumb|150px|''figure 2 (from reference <ref name="ref1" />).'']] |
Nucleotide sequence of Xa10 promoter and EBEavrXa10. The transcriptional initiation site is marked as ”+1”. Only a short functional region of Xa10 promoter (-220 to -1), the 5’ untranslated region (in italics), and start codon (in bold italics) are listed. EBEAvrAx10 is referenced. | Nucleotide sequence of Xa10 promoter and EBEavrXa10. The transcriptional initiation site is marked as ”+1”. Only a short functional region of Xa10 promoter (-220 to -1), the 5’ untranslated region (in italics), and start codon (in bold italics) are listed. EBEAvrAx10 is referenced. | ||
==References== | ==References== | ||
Latest revision as of 08:52, 1 June 2014
Function
Bacterial blight of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), is the most devastating disease of rice (Oryza sativa L). Rice lines that carry resistance (R) gene Xa10 confer race-specific resistance to Xoo strains harboring avirulence (Avr) gene avrXa10. The rice TAL effector-dependent resistance protein Xa10 trigger cell death and calcium depletion in the Endoplasmic Reticulum.Xa10 is a transcription activator-like (TAL) effector-dependent R gene for resistance to bacterial blight in rice (Oryza sativa). Xa10 contains a binding element for the TAL effector AvrXa10 (EBEAvrXa10) in its promoter(from reference [2]), and AvrXa10 specifically induces Xa10 expression. Expression of Xa10 induces programmed cell death in rice, Nicotiana benthamiana, and mammalian HeLa cells. The Xa10 gene product Xa10 localizes as hexamers in the endoplasmic reticulum (ER) and is associated with ER Ca (2+) depletion in plant and HeLa cells. Race-specific resistance to Xanthomonas oryzae pv. Oryzae conferred by bacterial blight resistance gene Xa10 in rice (Oryza sativa) involves accumulation of a lignin-like substance in host tissues. When seedling leaves of rice (Oryza sativa L.) cultivars carrying the Xa-10 gene for bacterial blight resistance were infiltrated with suspensions of cells from races 2 or 5 of Xanthomonas oryzae pv. Oryzae, a rapid, race-specific incompatible reaction occurred: the leaf tissue became dark greenish brown, and the rate of bacterial multiplication decreased compared to compatible interactions. By 48–72 h after inoculation, the affected area was dark brown. Lignin-like phenolic compounds accumulated throughout the inoculation site in the incompatible combination, beginning by 18–24 h after inoculation and reaching a maximum by 72 h.
Mutation
Xa10 variants that abolish programmed cell death and ER Ca (2+) depletion in N. benthamiana and HeLa cells also abolish disease resistance in rice. Rice gene variants can not resist the Bacterial blight of rice. Expression During infection, X.oryzae pv oryzae strains deliver members of the large AvrBs3-related effector family into host cells via the bacterial type III secretion system. AvrBs3-like effectors, also referred to as transcription activator- like (TAL) effectors, function as transcription factors and induce expression of specific host genes within the host cells. TAL effector-mediated host gene induction is determined by the repetitive central region of each effector, which consists of near-perfect direct repeats of 33-to 35-amino acid residues. The repetitive region determines the sequence specificity of the targeted DNA elements within the promoters of the affected genes. Strains of Xanthomonas use TAL effectors to induce host susceptibility (S) genes, which facilitate bacterial infection and promote diseases. Rice and pepper (Capsicum annuum) have evolved mechanisms of self-immolation by the adaptation of TAL effector-specific R genes. Individual TAL effectors can have dual functions in regulating host gene expression, serving as important virulence factors to induce S gene expression for susceptibility and serving as important factors triggering resistance in cultivars with cognate R genes.
Mechanism
Many R genes, upon perception of an avirulent pathogen(from reference [3]), trigger an HR by a mechanism involving cellular efflux of anions and potassium and influx of calcium and hydrogen ions. Following the ion flux, the affected cells generate an oxidative burst, producing re-active oxygen species (ROS).The ROS cause lipid peroxidation and oxidative damage to DNA and proteins, resulting in PCD and the formation of local lesions. The ROS burst also drives cross-linking of cell wall com-pounds and leads to expression of plant genes involved in cellular protection and defense. A broad range of R genes have been identified.
Revolution
The products of the TAL effector-dependent R genes show no apparent sequence similarities(from reference [4]).
Structure
Nucleotide sequence of Xa10 promoter and EBEavrXa10. The transcriptional initiation site is marked as ”+1”. Only a short functional region of Xa10 promoter (-220 to -1), the 5’ untranslated region (in italics), and start codon (in bold italics) are listed. EBEAvrAx10 is referenced.
References
[4]- ↑ 1.0 1.1 1.2 DongshengTian, JunxiaWang, XuanZeng, KeyuGu, ChengxiangQiu, et al. (2014) The Rice TAL Effector-Dependent Resistance Protein XA10 Triggers Cell Death and Calcium Depletion in the Endoplasmic Reticulum. Plant Cell 26: 497-515.
- ↑ 2.0 2.1 Abas, L., and Luschnig, C. (2010) Maximum yields of microsomal-type membranes from small amounts of plant material without requiring ultracentrifugation. Anal. Biochem. 401: 217-227.
- ↑ 3.0 3.1 Antonsson, B., etal. (1997) Inhibition of Bax channel-forming activity by Bcl-2. Science 277: 370-372.
- ↑ 4.0 4.1 Antony, G., Zhou, J., Huang, S., Li, T., Liu, B., White, F., and Yang, B. (2010). Rice xa13 recessive resistance to bacterial blight is defeated by induction of the disease susceptibility gene Os-11N3. Plant Cell 22: 3864-3876.
