What makes peppers blush

December 14, 2020

Visually, this transformation is clearly visible in the colour change from green to orange or red. The team documented the process in detail and globally at the protein level and published the results in "The Plant Journal" on 30 November 2020.

From chlorophyll to carotenoid

Because of their aromatic taste and high concentrations of health-promoting ingredients such as vitamin C and antioxidant provitamin A (carotenoids), bell peppers, scientifically Capsicum annuum, belong to the most popular vegetables. The ripening process in peppers proceeds from photosynthetically active fruits with high chlorophyll and starch content to non-photosynthetic fruits that are rich in carotenoids. Essential steps of this transformation take place in typical plant cell organelles, the so-called plastids.

Progenitor organelles, the so-called proplastids, are the first step. They are not yet differentiated and transform into different plastids depending on tissue type and environmental signals. In many fruit and vegetable varieties, the chromoplasts develop from them. "They got their name because of their frequently bright colours," explains Sacha Baginsky. In pepper fruits, proplastids initially turn into photosynthetically active chloroplasts, from which the carotenoid-rich chromoplasts develop through the breakdown of chlorophyll and the photosynthesis machinery as the fruit ripens.

The crucial difference to tomatoes

The same applies to tomatoes, although there is a crucial difference to peppers: tomatoes belong to the climacteric fruits that continue to ripen after harvesting. Biochemically, this process is characterised by an enormous increase in respiratory activity with high oxygen consumption, the so-called climacteric. This is not the case with peppers. "The green peppers frequently available in supermarkets are unripe," says Sacha Baginsky. They still carry chlorophyll-rich chloroplasts and, when the pepper is fresh, also contain a large amount of the photosynthetic storage substance starch. "Our data now show several differences in chromoplast differentiation between peppers and tomatoes at the molecular level, which provides insights into the different metabolism of climacteric and non-climacteric fruits," says the biologist.

One example is energy metabolism: the protein PTOX - acronym of plastid terminal oxidase - that generates water by transferring electrons to oxygen during carotenoid production is only present in small quantities in peppers. This might result in lower oxygen consumption and could be associated with increased ATP synthesis. Chromoplasts use modules of photosynthetic electron transport for ATP synthesis, which in peppers is at least partially carried out via the so-called cytochrome b6/f complex and plastocyanin that in peppers is present in large quantities - in contrast to tomatoes. Small amounts of PTOX in peppers could mean that more ATP can be produced as more electrons from carotenoid production flow via this pathway to a previously unknown oxidase.

More effective and sustainable production of carotenoids in plants

"This is just one example of several, sometimes subtle differences in the metabolism of tomato and pepper chromoplasts," explains Sacha Baginsky. "Our data provide a new approach to understanding chromoplast differentiation, which we now intend to explore in more depth." For example, the Bochum-based team will use a system described by a Spanish group in which chromoplast differentiation in leaves is induced by the production of a single enzyme. This could indicate ways to produce carotenoids more effectively and sustainably in plants. The data collected so far are publicly available through the Pride database.

The study was funded by the German Research Foundation, funding codes INST 271/283-1 FUGG and BA 1902/3-2.

Ruhr-University Bochum

Related Carotenoids Articles from Brightsurf:

How boundaries become bridges in evolution
The mechanisms that make organisms locally fit and those responsible for change are distinct and occur sequentially in evolution.

How plants protect themselves from sun damage
MIT chemists have observed, for the first time, one of the possible mechanisms that have been proposed for how plants dissipate energy when they are exposed to excess sunlight.

Gene responsible for lutein esterification in bread wheat identified
Researchers have identified and confirmed the gene responsible for lutein esterification in bread wheat.

Meatballs might wreck the anti-cancer perks of tomato sauce
Some of the anti-cancer benefits of tomatoes, specifically those from a compound called lycopene, could disappear when they're eaten with iron-rich foods, according to a new study from The Ohio State University.

Cooking vegetables: healthier with extra virgin olive oil
Cooking vegetables in the sofrito (sauté) with extra virgin olive oil favours the absorption and release of bioactive compounds of its traditional ingredients (garlic, onion and tomato), according to the study published in the journal Molecules about the role of gastronomy in the health-improving effects of the Mediterranean Diet.

What the vibrant pigments of bird feathers can teach us about how evolution works
A UA team shows that evolution is driven by dependency on other species within ecological communities - testing a long-held idea of the UA's late, great George Gaylord Simpson.

New study uncovers how lutemax 2020 protects the eyes against blue light damage
Morristown, N.J., June 29, 2018 - In a new study published in Nutrients titled 'Lutein and Zeaxanthin Isomers Protect Against Light-induced Retinopathy via Decreasing Oxidative and Endoplasmic Reticulum Stress in BALB/cJ Mice', Lutemax 2020 supplementation was shown to protect photoreceptors against blue light damage by mitigating oxidative and endoplasmic reticulum stress -- a primary mechanism associated with photoreceptor damage and visual impairment.

Healthy diet may lower eye disease risk
An analysis of recent high-quality research reveals that diet may affect individuals' risks related to the development and progression of age-related macular degeneration (AMD).

Deep-freezing of orange juice can increase the absorption of beneficial compounds
The cold treatments have two opposite effects. On one hand, they cause the carotenoids to degrade (negative effect) and, on the other hand, they generate an increase in the bioaccessibility of the carotenoids (positive effect).

Tomatoes of the same quality as normal, but using only half the water
When reducing the water used to water cherry tomato crops by more than 50%, the product not only maintains its quality, both commercially and nutritionally, but it also even increases the level of carotenoids, compounds of great interest in the food-processing industry.

Read More: Carotenoids News and Carotenoids Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.