Pattern analysis suggests that phosphopyruvate carboxylase in maturing soybean seeds promotes the accumulation of protein.

The protein and oil contents in soybean seeds are major factors in seed quality. Seed proteins and oils are synthesized from sucrose and nitrogenous compounds transported into maturing seeds. In this study, we compared changes in the activity of phosphopyruvate carboxylase (PEPC) and the accumulation profiles of protein and oil in maturing seeds of two soybean cultivars, which exhibit different protein and oil contents in seeds, to determine the interrelationships of them. A principal component analysis indicated a concordance of seed PEPC activity with the protein content, but did not with the oil content. PEPC activity per seed was highest in the late maturation stage, when the physiological status of the vegetative organs drastically changed. The high-protein cultivar had higher PEPC activity compared to the low-protein cultivar. These results highlight the biological role of PEPC in the synthesis of protein, therefore it was implied that PEPC could be a biomarker in soybean breeding. ANOVA: analysis of variance; DS: developmental stage; DW: dry weight; FW: fresh weight; NIR: near infrared; PEP(C): phosphopyruvate (carboxylase); PC(A): principal component (analysis); S.E.: standard error; WC: water content.