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PROTEIN L- ISOASPARTYL METHYLTRANSFERASE2 gene is differentially expressed in chickpea and enhances seed vigor and longevity by reducing abnormal isoaspartyl accumulation predominantly in seed nuclear proteins

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Title PROTEIN L- ISOASPARTYL METHYLTRANSFERASE2 gene is differentially expressed in chickpea and enhances seed vigor and longevity by reducing abnormal isoaspartyl accumulation predominantly in seed nuclear proteins
 
Creator Verma, Pooja
Kaur, Harmeet
Petla, Bhanu Prakash
Rao, Venkateswara
Saxena, Saurabh C.
Majee, Manoj
 
Subject Chickpea
Seed Vigor
Isoaspartyl
Seed Nuclear Proteins
 
Description Accepted date: January 1, 2013
PROTEIN l-ISOASPARTYL METHYLTRANSFERASE (PIMT) is a widely distributed protein-repairing enzyme that catalyzes the conversion of abnormal l-isoaspartyl residues in spontaneously damaged proteins to normal aspartyl residues. This enzyme is encoded by two divergent genes (PIMT1 and PIMT2) in plants, unlike many other organisms. While the biological role of PIMT1 has been elucidated, the role and significance of the PIMT2 gene in plants is not well defined. Here, we isolated the PIMT2 gene (CaPIMT2) from chickpea (Cicer arietinum), which exhibits a significant increase in isoaspartyl residues in seed proteins coupled with reduced germination vigor under artificial aging conditions. The CaPIMT2 gene is found to be highly divergent and encodes two possible isoforms (CaPIMT2 and CaPIMT2') differing by two amino acids in the region I catalytic domain through alternative splicing. Unlike CaPIMT1, both isoforms possess a unique 56-amino acid amino terminus and exhibit similar yet distinct enzymatic properties. Expression analysis revealed that CaPIMT2 is differentially regulated by stresses and abscisic acid. Confocal visualization of stably expressed green fluorescent protein-fused PIMT proteins and cell fractionation-immunoblot analysis revealed that apart from the plasma membrane, both CaPIMT2 isoforms localize predominantly in the nucleus, while CaPIMT1 localizes in the cytosol. Remarkably, CaPIMT2 enhances seed vigor and longevity by repairing abnormal isoaspartyl residues predominantly in nuclear proteins upon seed-specific expression in Arabidopsis (Arabidopsis thaliana), while CaPIMT1 enhances seed vigor and longevity by repairing such abnormal proteins mainly in the cytosolic fraction. Together, our data suggest that CaPIMT2 has most likely evolved through gene duplication, followed by subfunctionalization to specialize in repairing the nuclear proteome.
This work was supported by the Department of Biotechnology
(grant no. BT/PR10262/GBD/27/77/2007) and National Institute of
Plant Genome Research, Government of India, as well as by the University Grant Commission and Council of Scientific and Industrial
Research, Government of India, for research fellowships to P.V., H.K.,
B.P.P. and V.R.
 
Date 2015-11-24T10:13:50Z
2015-11-24T10:13:50Z
2013
 
Type Article
 
Identifier Plant Physiol., 161(3): 1141-1157
0032-0889
http://172.16.0.77:8080/jspui/handle/123456789/379
http://www.plantphysiol.org/content/161/3/1141.long
10.1104/pp.112.206243
 
Language en_US
 
Publisher American Society of Plant Biologists