Leaf permeasel Gene of Maize 1 s Required for Chloroplast Development

Adjacent bundle sheath and mesophyll cells cooperate for carbon fixation in the leaves of C4 plants. Mutants with compromised plastid development should reveal the degree to which this cooperation is obligatory, because one can assay whether mesophyll cells with defective bundle sheath neighbors retain C4 characteristics or revert to C3 photosynthesis. The leaf permeasel-mutablel (Ipel-ml) mutant of maize exhibits disrupted chloroplast ultrastructure, preferentially affecting bundle sheath choroplasts under lower light. Despite the disrupted ultrastructure, the metabolic cooperatian of bundle sheath and mesophyll cells for C4 photosynthesis remains intact. To investigate this nove1 mutation, t h e k t i v a tor transposon-tagged allele and cDNAs corresponding to the Lpel mRNA from wild-type plants wers cloned. The Lpel gene encodes a polypeptide with significant similarity to microbial pyrimidine and purine transport proteins. An analysis of revertant sectors generated by Activator excision suggests that the Lpel gene product is cell autonomous and can be absent up to the last cell divisions in the leaf primordium without blocking bundle sheath chloroplast development.