P61 Protein from a Male Sterile Mutant of Rice is an Isoform of the Chloroplast ATPase β Subunit

P61 was a protein identified from chloroplasts of Nongken 58S, a male sterile mutant of rice ( Oryza sativa L. ssp. japonica ). Microsequence analysis has revealed that its N_terminal sequence was identical to N_termini of ATPase β subunits of chloroplasts from rice and barley. The antiserum produced using ATPase β subunit from maize specifically recognized P61. P61 had the same molecular weight as the chloroplast ATPase β subunit of wild_type rice “Nongken 58”, but had different isoelectric point (pI) from this β subunit. P61 was more basic than this β subunit. Thus, P61 would be identified as an isoform of the chloroplast ATPase β subunit of rice, named β 1. Genetic analysis with a F 2 population of Nongken 58SדNongken 58” showed that a single recessive genic gene regulated the formation of β 1.