IDENTIFICATION OF PEROXISOME MEMBRANE-PROTEINS (PMPS) IN SUNFLOWER (HELIANTHUS-ANNUUS L) COTYLEDONS AND INFLUENCE OF LIGHT ON THE PMP DEVELOPMENTAL PATTERN

Boundary membranes were recovered from glyoxysomes, transition peroxis omes, and leaf-type peroxisomes purified from cotyledons of sunflower (Helianthus annuus L.) at three stages of postgerminative growth. Afte r membranes were washed in 100 mM Na2CO3 (PH 11.5), integral peroxisom e membrane proteins (PMPs) were solubilized in buffered aminocaproic a cid/dodecyl maltoside (0.63 M/1.5%) and analyzed by nondenaturing and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Six p rominent nondenatured PMP complexes and 10 prominent SDS-denatured pol ypeptides were identified in the membranes of the three types of perox isomes. A nondenatured complex of approximately 140 kD, composed mainl y of 24.5-kD polypeptides, decreased temporally, independently of seed ling exposure to white, blue, or red light; only far-red light seemed to prevent its decrease. PMP complexes of approximately 120 and 70 kD, in contrast, were present at all stages and changed in polypeptide co ntent. It remains to be determined whether these data reflect changes within in vivo complexes or within complexes formed following/during d etergent solubilization. Conversion of glyoxysomes to leaf-type peroxi somes in white or red light after a 2-d dark period was accompanied by the appearance of three SDS-denatured PMPs: 27.5, 28, and 47 kD. The former two became part of the PMP120 and 70 complexes, as well as part of a new PMP130 complex that also possessed the PMP47. Growth of seed lings in blue or far-red light did not promote the appearance of PMPs 27.5 or 28. Blue light promoted the appearance of PMP47, and far-red l ight seemed to prevent its appearance. Chlorophyll likely is not the p hotoreceptor involved in accumulation of PMPs because the PMP composit ion is distinctly different in seedlings irradiated with red or blue l ight of comparable fluence rates. Several lines of evidence indicate t hat the synthesis and acquisition of membrane and all matrix proteins are not coupled. The data provide evidence for a change in PMP composi tion when sunflower or any other oilseed glyoxysomes are converted to leaf-type peroxisomes and suggest that the change is regulated by both photobiological and temporal mechanisms.