Development and regulation of three glyoxysomal enzymes during cotton seed maturation and growth

Abstract

The temporal, nonconcerted development of activities of malate synthase (MS), isocitrate lyase (ICL), and catalase (Cat) was explored in more detail in maturing and germinated cotton (Gossypium hirsutum L.) seeds. RNA was extracted at six intervals beginning at 17 days post anthesis (DPA) through 72 hours post imbibition (HPI). In vitro translations revealed that mRNAs for each enzyme were translatable at all intervals. Enzyme activities and immunoselected proteins also were found at all intervals. Similar specific activities throughout maturation indicated that embryo cells were not accumulating inactive protein. The steady-state level of mRNAs encoding each enzyme exhibited different patterns of change during seed maturation, and each peaked at least 24 h before peak enzyme activities in germinated seeds. All three enzymes occur together as early as 17 DPA in a coordinate manner; however, the subsequent, nonconcerted increases in protein, activity, and mRNA for each enzyme indicate that developmental expression in cotton seed embryos is regulated in a noncoordinate fashion by as yet unidentified specific control mechanism(s).