Developmental, tissue-specific, and environmental factors regulate the biosynthesis of N-acylphosphatidylethanolamine in cotton (Gossypium hirsutum L)

N-Acylphosphatidylethanolamine (NAPE) is an acylated derivative of the common membrane phospholipid, phosphatidylethanolamine (PE). NAPE is synthesized in cotton cotyledons from PE and free fatty acids by a membrane-bound enzyme designated NAPE synthase (Chapman and Moore, 1993). In the present study, a comprehensive time-course of NAPE synthase activity was determined for cotton cotyledons at various stages of development including embryogenesis, desiccation, germination, seedling growth, and senescence. Specific activities of NAPE synthase were highest in cotyledons of embryos at 25 days after anthesis (DAA) and 12-h-old seedlings; however, on a per cotyledon basis, activities were more than ten times higher in cotyledons of germinating seeds than in cotyledons of-developing seeds. NAPE synthase activity declined rapidly when seedlings were exposed to light (but not when seedlings were kept in the dark). NAPE content in cotyledons increased concomitant with PE and total phospholipid content during seed germination and the first 48 h of seedling growth in the dark. NAPE synthase activity was substantially different in different organs of 14-d-old cotton seedlings; specific activities were highest in plumules (more than an order of magnitude higher than specific activities in fully expanded cotyledons or mature leaves of older plants). NAPE content in different organs of 14-d-old seedlings ranged from 1.9 % (mol % total phospholipid) in cotyledons to 3.2 % in plumules and was highest in organs that contained the highest NAPE synthase activity. Switching 1-d-old cotton seedlings to different temperatures for 24 h had a dramatic effect on NAPE synthase specific activity. Specific activity in cotyledons was more than 2-fold higher at cooler growth temperatures (20 degrees C) than warmer growth temperatures (40 degrees C). Together, our results indicate that NAPE biosynthesis is regulated by developmental, tissue-specific, and environmental factors.