Srivastava V, Srivastava MK, Chibani K, Nilsson R, Rouhier N, Melzer M, Wingsle G
Alternative splicing studies of the reactive oxygen species gene network in Populus reveal two isoforms of high-isoelectric-point superoxide dismutase
Plant Physiology: 2009 149:1848-1859
Recent evidence has shown that alternative splicing (AS) iswidely involved in the regulation of gene expression, substantiallyextending the diversity of numerous proteins. In this study,a subset of expressed sequence tags representing members ofthe reactive oxygen species gene network was selected from thePopulusDB database to investigate AS mechanisms in Populus.Examples of all known types of AS were detected, but intronretention was the most common. Interestingly, the closest Arabidopsis(Arabidopsis thaliana) homologs of half of the AS genes identifiedin Populus are not reportedly alternatively spliced. Two genesencoding the protein of most interest in our study (high-isoelectric-pointsuperoxide dismutase [hipI-SOD]) have been found in black cottonwood(Populus trichocarpa), designated PthipI-SODC1 and PthipI-SODC2.Analysis of the expressed sequence tag libraries has indicatedthe presence of two transcripts of PthipI-SODC1 (hipI-SODC1band hipI-SODC1s). Alignment of these sequences with the PthipI-SODC1gene showed that hipI-SODC1b was 69 bp longer than hipI-SODC1sdue to an AS event involving the use of an alternative donorsplice site in the sixth intron. Transcript analysis showedthat the splice variant hipI-SODC1b was differentially expressed,being clearly expressed in cambial and xylem, but not phloem,regions. In addition, immunolocalization and mass spectrometricdata confirmed the presence of hipI-SOD proteins in vasculartissue. The functionalities of the spliced gene products wereassessed by expressing recombinant hipI-SOD proteins and invitro SOD activity assays.
E-link to journal