水稻含錳超氧歧化?t於聚丙烯醯胺電泳分離後該酵素素活性具多型性。從水稻 cDNA 庫篩選得到兩個含錳超氧歧化?t之全長cDNA（951，1352 bp），其彼此間之全長和碼定蛋白質對應序列，分別具85.27%和98.71% 相似；而比較二者5'UTR和3'UTR序列，各有59.29%和85.92%相似。南方轉印結果顯示水稻含錳超氧歧化?t為多基因族。

　　　　　There are multiple forms of manganese superoxide dismutase (Mn-SOD) in rice extract, which can be separated by native gel electrophoresis. We have isolated two rice cDNA clones encoding Mn-SOD designed as msod1 and msod2. The two clones contain 951 and 1352 bps with sequence identity of 85.27% in full length and 98.71% in the coding region. However, the 5' regions prior to the first in-frame start codon (113bp in msod1 and 511bp in msod2) are only 59.29% identical, but the 3' untranslated regions (142bp in msod1 and 145bp in msod2) share 85.92% similarity. Genomic Southern analysis indicates that multiple genes encoding Mn-SOD in rice are multiple in nature.