Two Oleosins Expressed in the Mesocarp of Native Mexican Avocado, Key Genes in the Oil Content
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ORIGINAL PAPER
Two Oleosins Expressed in the Mesocarp of Native Mexican Avocado, Key Genes in the Oil Content Fernando Sánchez-Albarrán 1 & Luis María Suárez-Rodríguez 1 Joel Edmundo López-Meza 2 & Rodolfo López-Gómez 1
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León Francisco Ruíz-Herrera 1
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Accepted: 30 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Intracellular lipid droplets (LD) provide the oil storage mechanism of plants. They are found within seeds as individual structures, even under conditions of cold stress and dehydration, due to the protein that covers them. This protein, called oleosin, is found exclusively in plants and has been widely studied in seeds. Avocado fruits (Persea americana Mill.) are rich in oil, which is stored in the mesocarp, not in the seeds. The presence of oleosin in the mesocarp tissue of avocadoes has been reported, but its physiological role is still unknown. In this study, we identify two genes that code for oleosin in the mesocarp of the native Mexican avocado. These sequences are very different from those of seed oleosins. Both genes are expressed during fruit ripening, while one, PaOle1, has the highest expression in the green fruit stage. The protein of PaOle1 is stable during the fruit ripening process and covers all the mesocarp LDs. The expression of PaOle1 gene and protein is organ specific to avocado mesocarp. Among avocadoes varieties oleosin abundance is directly related to oil content. Keywords Avocado . Drymifolia . Oleosin . Lipid droplet
Introduction Oleosins are small proteins measuring 17 to 25 kDa, found exclusively in plants. They are involved in stabilizing lipid storage and have a hydrophobic hairpin with a proline knot in the middle. The carboxyl and amino terminal regions give them an electrostatic charge density that is transferred to the lipid droplets. This charge is responsible for avoiding coalescence of LDs [1]. Oleosins have been thoroughly described in seed tissues, where they are the principal element responsible for maintaining the integrity and the size of LDs through dehydration, vernalization and rehydration before germination
* Rodolfo López-Gómez [email protected] 1
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico
2
Centro Multidisciplinario de Estudios en Biotecnología, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico
[2]. Oleosins evolved from similar oleo-like proteins that are present in unicellular algae. The first oleosins are characterized by the presence of low-expression codifying oleosin transcripts in chlorophytes (Chlamydomonas reinhardtii), and its protein are detectable in the LDs of charophytes (Spirogyra grevilleana) [3]. Research has identified five welldifferentiated lineages of these proteins: 1) primitive oleosins (P), from algae, mosses and ferns; 2) universal oleosins (U), found in all terrestrial plants; 3) low molecular weight oleosins (SL), on seeds from gymnosperms to angiosperms; 4) high molecular
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