Brassica rapaHas Three Genes That Encode Proteins Associated with Different Neutral Lipids in Plastids of Specific Tissues

Abstract

Plastid lipid-associated protein (PAP), a predominant structural protein associated with carotenoids and other non-green neutral lipids in plastids, was shown to be encoded by a single nuclear gene in several species. Here we report three PAP genes in the diploid Brassica rapa; the three PAPs are associated with different lipids in specific tissues. Pap1 and Pap2 are more similar to each other (84% amino acid sequence identity) than to Pap3 (46% and 44%, respectively) in the encoded mature proteins. Pap1 transcript was most abundant in the maturing anthers (tapetum) and in lesser amounts in leaves, fruit coats, seeds, and sepals; Pap2 transcript was abundant only in the petals; and Pap3 transcript had a wide distribution, but at minimal levels in numerous organs. Immunoblotting after sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that most organs had several nanograms of PAP1 or PAP2 per milligram of total protein, the highest amounts being in the anthers (10.9 g mg Ϫ1 PAP1) and petals (6.6 g mg Ϫ1 PAP2), and that they had much less PAP3 (Ͻ0.02 g mg Ϫ1 ). In these organs PAP was localized in isolated plastid fractions. Plants were subjected to abiotic stresses; drought and ozone reduced the levels of the three Pap transcripts, whereas mechanical wounding and altering the light intensity enhanced their levels. We conclude that the PAP gene family consists of several members whose proteins are associated with different lipids and whose expressions are controlled by distinct mechanisms. Earlier reports of the expression of one Pap gene in various organs in a species need to be re-examined.

Dual targeting of a mature plastoglobulin/fibrillin fusion protein to chloroplast plastoglobules and thylakoids in transplastomic tobacco plants

“…Although plastoglobulins associate with lipid bodies and membranes (Lundquist et al 2012), their overall amino acid composition is not hydrophobic and it is apparent from hydropathy plots that, unlike oleosin, they lack a strongly hydrophobic structural element. Therefore, association of PGLs with plastoglobules probably involve interactions with the polar head group of membrane lipids at the plastoglobule surface (Kim et al 2001). Apart from a ''bona fide'' thylakoid localization, the strong overexpression of PGL35-HIVp24 may saturate the binding sites at the surface of the plastoglobules and force a larger proportion to associate with the thylakoids.…”

Ubiquitous and Endoplasmic Reticulum–Located Lysophosphatidyl Acyltransferase, LPAT2, Is Essential for Female but Not Male Gametophyte Development in Arabidopsis

“…Results of control experiments with antibodies against other organelle markers reaffirm that BrLPAT2 was colocated with calreticulin in the ER in Brassica tapetum cells. For example, the plastid protein, plastid lipid-associated protein (Kim et al, 2001), was localized in the plastids independent of the calreticulin in the ER ( Figure 8C). …”

Plastoglobules: versatile lipoprotein particles in plastids

“…In addition, the expression of PGL genes has been shown to be modulated by diverse stress stimuli such as exposure to reactive oxygen species [48,49] or ozone [50], ABA induction [51,52], wounding [3,48,50,53], bacterial infection [49] and a variety of other environmental stress conditions [3,48,50,51,[53][54][55]. Systematic and quantitative comparative proteomics have shown that the predominant change in the Arabidopsis peripheral thylakoid proteome upon light stress treatment is the several-fold up-regulation of plastoglobule associated proteins [56].…”