CaAlaAT1 catalyzes the alanine: 2-oxoglutarate aminotransferase reaction during the resistance response against Tobacco mosaic virus in hot pepper.
Hot pepper (Capsicum annuum L. cv. Bugang) plants exhibit a hypersensitive response (HR) upon infection by Tobacco mosaic virus (TMV) pathotype P0. To elucidate molecular mechanism that underlies this resistance, hot pepper cv. Bugang leaves were inoculated with TMV-P0 and genes specifically up-regulated during the HR were isolated by differential screening. One of the clones, CaAlaAT1 encoding a putative alanine aminotransferase (EC 2.6.1.2) exhibited organ-specific expression pattern and the transcript accumulated abundantly in red (ripe) fruit tissues. CaAlaAT1 transcript was also induced in older leaves during senescence. The expression of CaAlaAT1 gene was increased in the incompatible interaction with TMV-P0 but was not in the compatible interaction with TMV-P1.2. When a strain of Xanthomonas campestris pv. vesicatoria (Xcv) carrying an AvrBs2 gene was infiltrated into the leaves of a pepper cv. ECW 20R carrying Bs2 resistance gene, a marked induction and maintenance of CaAlaAT1 gene expression was observed. The expression of CaAlaAT1 gene was triggered by salicylic acid (SA) and ethylene but not by methyl jasmonate (MeJA). CaAlaAT1 seemed to be localized mostly at the cytosol from the polyethylene glycol (PEG)-mediated transformation experiment. CaAlaAT1 seemed to catalyze alanine: 2-oxoglutarate aminotransferase (AKT) reaction, which was a main activity among the four activities in vitro, during the resistance response against TMV in hot pepper. These results suggest that CaAlaAT1, a protein known to be involved in metabolic reactions, might be one of the components in the plant's defense signal pathway against pathogens.
Kim
Ki-Jeong
KJ
School of Life Sciences and Biotechnology, Korea University, 1, 5-ga, Anam-dong, Sungbuk-gu, Seoul, 136-701, Republic of Korea.
Park
Chang-Jin
CJ
An
Jong-Min
JM
Ham
Byung-Kook
BK
Lee
Boo-Ja
BJ
Paek
Kyung-Hee
KH
D000410:Alanine Transaminase / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002212:Capsicum / Q000201:enzymology* / Q000276:immunology / Q000382:microbiology / Q000821:virology*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007113:Immunity, Innate / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology / Q000821:virology*; D017386:Sequence Homology, Amino Acid; D014027:Tobacco Mosaic Virus / Q000276:immunology*; D015854:Up-Regulation; D044184:Xanthomonas vesicatoria / Q000502:physiology
D000410:Alanine Transaminase