Wayne Zita
Abstract:
Tomato (Solanum lycopersicum) is an excellent model crop to study biogenesis of carotenoids of chromoplasts [1]. The most abundant carotenoid accumulated in tomato fruits' chromoplast is Lycopene, this compound is responsible for the hallmark red color of the ripe fruit hence marking the completion of the chromoplast biogenesis. Lycopene biosynthesis in tomato is regulated at different levels but whether it depends also on retrograde signals is currently unknown. Recent studies have shown that tomato carotenoids accumulate in crystalline bodies and to a lesser extent in plastid lipid droplets (plastoglobules; PG). However, PGs are not simply lipid storage compartments. PG have a small proteome (of ~30 proteins) composed of structural proteins (fibrillins), enzymes mostly involved in prenyl lipid metabolism as well as atypical kinases with regulatory functions (ABC1K) [2, 3]. We investigate the PG proteome in mature tomato fuits. The major components are common with the red bell pepper PG proteome and include carotenoid enzymes like ZDS, LYC-β and CrtB. In addition, we identified a member of the ABC1K family: ABC1K1/PGR6. This protein has been described as a regulator of photosynthesis and carotenoid biosynthesis in Arabidopsis [3, 4]. By using a knock-out mutant, here we show the central role played by ABC1K1 in chromoplast development.
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Reference:
1. Simkin AJ, Gaffé J, Alcaraz JP, Carde JP, Bramley PM, Fraser PD, Kuntz M. Fibrillin influence on plastid ultrastructure and pigment content in tomato fruit. Phytochemistry. 2007 Jun;68(11):1545-56. doi: 10.1016/j.phytochem.2007.03.014. Epub 2007 Apr 26. PMID: 17466343.
2. Ytterberg AJ, Peltier J-B, van Wijk KJ (2006) Protein Profiling of Plastoglobules in Chloroplasts and Chromoplasts. A Surprising Site for Differential Accumulation of Metabolic Enzymes. 140 (3):984-997. doi:10.1104/pp.105.076083 %J Plant Physiology
3. Lundquist PK, Poliakov A, Bhuiyan NH, Zybailov B, Sun Q, van Wijk KJ (2012b) The functional network of the Arabidopsis plastoglobule proteome based on quantitative proteomics and genome-wide coexpression analysis. Plant Physiol 158 (3):1172-1192. doi:10.1104/pp.111.193144
4. Pralon T, Shanmugabalaji V, Longoni P, Glauser G, Ksas B, Collombat J, Desmeules S, Havaux M, Finazzi G, Kessler F (2019) Plastoquinone homoeostasis by Arabidopsis proton gradient regulation 6 is essential for photosynthetic efficiency. Communications Biology 2 (1):220. doi:10.1038/s42003-019-0477-4
