An event of alternative splicing affects the expression of the NTRC gene, encoding NADPH-thioredoxin reductase C, in seed plants

Abstract

The NTRCgene encodes aNADPH-dependentthioredoxin reductase with a joint thioredoxin domain, exclusive ofphotosynthetic organisms. An updated search of NTRCgenesshows that althoughmost species harbor a single copyof the NTRC gene, two copieswere identified in different species of the genus Solanum, Glycine maxand the moss Physcomitrella patens. The phylogenetic analysis of NTRCs from different sources produced a tree with the major groups of photosynthetic organisms: cyanobacteria, algae and land plants, indicating the evolutionary success oftheNTRCgeneamong photosynthetic eukaryotes. An event of alternative splicingaffecting the expression of the NTRCgene was identified, which is conserved in seed plants but not in algae, bryophytes and lycophytes. The alternative splicingevent resultsina transcript with premature stop codon, which would produce atruncated form of the enzyme. The standard splicing/ alternative splicing(SS/AS)transcriptsratio was higher in photosynthetic tissues from Arabidopsis, Brachypodiumand tomato, in line with thehigher content of the NTRCpolypeptide in these tissues. Moreover, environmental stresses such as coldor high salt affected the SS/AS ratio of the NTRC gene transcripts in Brachypodiumseedlings.These results suggest that the alternative splicing of the NTRCgenemight be an additional mechanism for modulating the content of NTRC in photosynthetic and non-photosynthetic tissuesof seed plants.