Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 21, 2005
Publication Date: March 1, 2006
Citation: Baek, K., Skinner, D.Z., Ling, P., Chen, X. 2006. Molecular structure and organization of the wheat genomic manganese superoxide dismutase gene. Genome 49:209-218. Interpretive Summary: One of the challenges faced by plants exposed to various stresses is the accumulation of reactive oxygen species, damaging chemicals that are produced by the plants themselves. Plants have developed a number of defense mechanisms in response to these chemicals. One of these defense mechanisms are antioxidant enzymes. The most efficient antioxidant enzyme is manganese superoxide dismutase (MnSOD). We studied the physical structure of a gene from wheat that encodes the MnSOD enzyme. We found that the gene contains several elements that enable it to respond to several stress factors, such as cold temperature, drought, salt, and high light. Other elements were found that enable the gene to respond to plant hormones. These results suggest MnSOD is an integral part of a plant's response to numerous stress factors, responding to the stresses directly and to signals from hormone pathways. This information suggests selecting wheat plants for optimized MnSOD activity would contribute to more stress-tolerant wheat varieties.
Technical Abstract: The genomic structure of an MnSOD gene in wheat was elucidated by sequencing a clone from a BAC library of a stripe-rust resistant wheat line. The clone was identified by hybridization with a wheat MnSOD cDNA. The gene consisted of six exons interrupted by five introns with a total length of 4773 nucleotides from the start codon to the termination codon. The wheat MnSOD gene was the longest among those sequenced from plant species. The transcription initiation site was preceded by a G+C-rich promoter without a TATA or CAAT box. The promoter contained many putative cis-acting regulatory elements including an ABA-responsive element, stress-responsive element, and GC-repeat, and several other structural features in common with the promoter of the rice MnSOD gene. A Stowaway-like transposable element was found in intron 5 of the wheat MnSOD gene, but further investigation revealed the transposable element was not present in all copies of the MnSOD genes.