Biochemical Studies on the Iojap Mutant of Maize

The white leaf tissue of seedlings of Zea mays L. affected by the recessive nuclear gene iojap shows no photosynthetic activity; it contains about 1.4% of carotenoid and less than 0.1% of chlorophyll a content of normal green tissue. Neither fraction I protein nor chloroplast adenosine triphosphatase (EC 3.6.1.4) (CF(1)) is detectable. This confirms earlier observations that plastids of white sectors of iojap maize do not contain ribosomes. About 40% of the activity of phosphoenolpyruvate carboxylase (EC 4.1.1.31) in green leaves could be found in white leaves indicating that the phosphoenolpyruvate carboxylase EC 4.1.1.31 is made on cytoplasmic ribosomes. The oxygen consumption of iojap-affected leaves is decreased.