Researchers Seek Better Understanding of Olive Drupe Development

By studying the molecular and physiological profiles of the drupes during the stages of development, researchers hope to optimize olive oil and table olive production.

Aug. 2, 2021
By Paolo DeAndreis

Recent News

Newly pub­lished research in Greece is paving the way to a deeper under­stand­ing of olive drupe ripen­ing.

Scientists at the Aristotle University of Thessaloniki inves­ti­gated how the mol­e­c­u­lar and phys­i­o­log­i­cal pro­files of olive dru­pes change as they go through the ripen­ing process.

This knowl­edge paves the way for fur­ther research, for exam­ple with breed­ing pro­grams, and pro­vides new insights into the final qual­ity fea­tures of the fruits.- Evangelos Karagiannis, researcher, Aristotle University of Thessaloniki

The researchers hope that a bet­ter under­stand­ing of ripen­ing will help farm­ers make the best deci­sions for plant­ing table olive and olive oil-pro­duc­ing vari­eties. The sci­en­tists explained that one of the project’s main goals is to help develop the Greek coun­try­side while pro­mot­ing the inter­ests of pro­duc­ers and con­sumers.

See Also: European Project Studies Olive Genetics to Prepare Growers for The Future

At the same time, empha­sis is placed on plant pro­tec­tion and the fight against impor­tant ene­mies of the olive tree,” Evangelos Karagiannis, who led the research team, told Olive Oil Times.

The researchers empha­sized that olive devel­op­ment is a com­plex bio­log­i­cal process that affects the human diet, and their study aimed to under­stand the mol­e­c­u­lar basis of olive qual­ity bet­ter.

This means that by deploy­ing high-through­put analy­ses, such as liq­uid chro­matog­ra­phy or gas chro­matog­ra­phy-mass spec­trom­e­try tech­niques and oth­ers, we obtain novel pro­teomic [the large-scale study of pro­teins] and metabolomic data,” Karagiannis said.

This pro­vides new knowl­edge about the mol­e­c­u­lar and phys­i­o­log­i­cal pro­file of the olive dur­ing drupe devel­op­ment,” he added. This knowl­edge paves the way for fur­ther research, for exam­ple with breed­ing pro­grams, and pro­vides new insights into the final qual­ity fea­tures of the fruits.”

According to the researchers, mul­ti­level stud­ies inte­grat­ing olive tran­scrip­tomics (the study of an organism’s RNA), pro­teomics and metabolomics are still lack­ing.

Such an ana­lyt­i­cal approach will pro­vide an enor­mous amount of data that expands our knowl­edge in the olive devel­op­ment and mat­u­ra­tion process,” the researchers wrote.

The first metabolomic inves­ti­ga­tion con­ducted by the Greek researchers focused on the Chondrolia Chalkidikis cul­ti­var.

This cul­ti­var is char­ac­ter­ized by its big and green olives that are har­vested by hand,” Karagiannis said. It was selected because it is wide­spread in north­ern Greece. Its dru­pes were mainly picked dur­ing the green-mature stage right before they turned pur­ple.”

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Those fruits were then exam­ined in six sub­se­quent stages of ripen­ing. The amount of pri­mary and sec­ondary metabo­lites and pro­teins were iden­ti­fied, and how they changed through­out the ripen­ing process was also observed.

We obtained a metabolomic and pro­teomic pro­file of Chondrolia Chalkidikis at the green-mature and pur­ple-turn­ing-black stages, which are the stages mostly used for both table olive and olive oil pro­duc­tion,” Karagiannis said. This allowed us to under­stand the rel­e­vant bio­chem­i­cal path­ways asso­ci­ated with the devel­op­ment process.”

More specif­i­cally, this approach will pro­vide new insights and update our cur­rent knowl­edge on the impor­tant role of pro­teins and metabo­lites in drupe devel­op­ment and ripen­ing, and thus would pro­vide a basis for fur­ther study on olive ripen­ing biol­ogy,” he added.

The olive fruit ripen­ing tran­si­tion from the green-mature to the pur­ple-turn­ing-black stage trig­gers numer­ous phe­no­typ­i­cal and phys­i­o­log­i­cal changes – for exam­ple, the soft­en­ing of the drupe. It also leads to changes at the mol­e­c­u­lar level, such as car­bo­hy­drate reg­u­la­tion.

According to the results of our study, at the pur­ple-turn­ing-black stage, the main high­lights are car­bo­hy­drate metab­o­lisms, such as cel­lobiose and galac­tose, and oleu­ropein accu­mu­la­tion,” Karagiannis said. On the other hand, at the green-mature stage, sev­eral pho­to­syn­thetic-related pro­teins were sig­nif­i­cantly up-reg­u­lated.”

This result clearly indi­cates the direct con­nec­tion between the phe­no­typ­i­cal char­ac­ter­is­tics of the olives – for instance, their green color – with changes in the mol­e­c­u­lar-bio­log­i­cal level, such as the increase of the pho­to­syn­thetic pro­teins,” he added.

At the cur­rent research stage, sci­en­tists are inves­ti­gat­ing how much the observed metabolomic shifts dur­ing ripen­ing depend on fac­tors such as the cul­ti­var or the tree’s loca­tion.

Both metabolomic and pro­teomic shifts depend greatly on dis­tinct para­me­ters such as the eval­u­ated cul­ti­var, grow­ing loca­tion, ter­rain, water sup­ply, stage of devel­op­ment and so on,” Karagiannis said.

For instance, it is known that oleu­ropein is the most accu­mu­lated com­pound in olive dru­pes,” he added. However, in green-col­ored olive cul­ti­vars at har­vest period, oleu­ropein con­cen­tra­tion could remain at high lev­els or may fall to zero at full mat­u­ra­tion in some pur­ple-black-col­ored cul­ti­vars.”

Moreover, it is worth men­tion­ing that most of the olive devel­op­men­tal-related stud­ies are mainly focus­ing on the sec­ondary metab­o­lism, with­out pro­vid­ing cer­tain infor­ma­tion about the pri­mary metab­o­lism, which is directly involved in fruit’s nor­mal growth and devel­op­ment,” Karagiannis con­tin­ued.

Overall, the researchers observed sev­eral key changes of the pro­teins and the metabo­lites they believe lay the ground­work for fur­ther stud­ies to under­stand olive fruit devel­op­ment bet­ter.

This study uncov­ered the impor­tant role of pro­teins and metabo­lites that are asso­ci­ated with drupe devel­op­ment and would pro­vide a basis for fur­ther study on olive biol­ogy,” the researchers con­cluded.





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