The distribution of protochlorophyllide and chlorophyll within seedlings of the lip1 mutant of Pea

The distribution of protochlorophyllide (Pchlide) and NADPH-Pchlideoxidoreductase (POR) was characterized in the epicotyls androots of wild-type pea (Pisum sativum L. cv. Alaska) and lip1,a mutant with light-independent photomorphogenesis caused bya mutation in the COP1 locus. The upper part of the dark-grownlip1 mutant epicotyls had a high Pchlide content that decreaseddownward the organ. The elevated Pchlide level in lip1 seedlingswas a result of the differentiation of more proplastids intoPchlide-containing plastids. The cortex cells in the lip1 epicotylwere filled with such plastids in contrast to the cortex cellsof wild-type seedlings. The mutant also developed Pchlide-containingplastids in the roots, indicating the suppressing effect ofthe COP1 locus on development of plastids in the correspondingtissues in dark-grown wild-type plants. The distribution ofPchlide-containing plastids in dark-grown lip1 mutant stem androot was similar to the distribution of chloroplasts in irradiatedwild-type plants. Both wild-type and lip1 epicotyls containedmostly short wavelength Pchlide fluorescing at 631 nm withonly a small shoulder at 654 nm, which was transformedto a minute amount of chlorophyllide (Chlide) by flash irradiation.In contrast, with continuous irradiation a considerable amountof Chlide was formed especially in the lip1 epicotyls. Immunoblotsindicated the presence of POR, as a 36 kDa band, in epicotylsof both dark-grown wild-type and lip1 mutant seedlings. However,lip1 stem tissue had a higher content of POR than the wild-typepea. The high content of POR was unexpected as lip1 lacked boththe 654 nm fluorescing Pchlide form and the regular PLBs.In light, a significant amount of chlorophyll was formed alsoin the roots of the lip1 seedlings. ³ Corresponding author: E-mail, mahdi.seyedi@molbio.gu.se; Fax,+46-31-773-2626.