The chloroplast terminal oxidase is involved in multiple physiological responses

A recent mutant screen has identified many new immutans (im) alleles that have distinct physiological differences in variegation severity. Many of the new mutants exhibit a less severe variegated phenotype than the extensively studied im allele spotty. These mutants have been characterized by crosses to wild type and spotty, Northern analysis, Western analysis, chlorophyll and carotenoid content and DNA sequencing. The alleles V189, cs3157, cs3639, cs3630 and cs3627 contain intronic mutations that cause aberrant im mRNA products to be formed. These aberrations in splicing can be described as intron inclusion, exon skipping and activation of cryptic splice sites. It is yet undetermined why these mutants show a variable severity of phenotype, as they are all null for the IM protein, but some early crosses suggest that the yellow seed phenotype of cs3630 may suppress the variegation caused by its im lesion. Alleles cs3628, cs3643 and cs3660 also show this yellow seed phenotype and have a less severe variegated phenotype.