Chemistry of plants

A group of researchers is concentrating its efforts, until 2015, on explaining the main causes of metabolic diversity of angiosperms.

By Fábio de Castro (SP)

Agência FAPESP – “An abominable mystery.” This is how Charles Darwin referred to the absence of an explanation for the explosion of angiosperms 140 million years ago. The origin and immense diversity of this primitive group of plants remain obscure to scientists until today.

Motivated by those fundamental scientific questions, a group of researchers is concentrating its efforts, until 2015, on explaining the main causes of metabolic diversity of angiosperms, including their regulation and the biochemical mechanisms involved in the production of substances by these plants’ metabolisms.

The Thematic Project “Molecular diversity among basal angiosperms” is part of BIOTA-FAPESP Program and was started a little over a year ago by its coordinator, Massuo Kato, professor at the Universidade de São Paulo (USP)’s Institute of Chemistry (IQ). Kato spoke about the project on July 4th in São Carlos (SP) at the 7th Symposium of the BIOTA-FAPESP Program.

The event, where both scientists and students participated, was held in conjunction with the 7th BIOTA-FAPESP Program Evaluation Meeting and the BIOprospecTA Evaluation Meeting, which comprise presentations of all participating projects in the program to an international committee of evaluators.

The model found to study the chemical ecology of angiosperms is the Piperaceae family, whose most well-known species is black pepper. According to Kato, piperaceae produce secondary metabolites which have great potential for biological activity. But little is known about the biosynthesis of these substances and their usefulness for the plant organisms themselves.

“The focus in a primitive group like the angiosperms is justified in a number of ways. One of them is that its origin still isn’t very clear. Even with the vertiginous increase of genetic information, Darwin’s ‘abominable mystery’ still hasn’t been solved. We don’t know, for example, if the diversification process of angiosperms is related to secondary metabolism, providing resistance and defense against insects, for example,” Kato told Agência FAPESP.

Aside from the gaps in knowledge about angiosperms, Kato had another strong reason to leave bioprospecting as second priority and focus his work on basic plant research: the direct influence of chemist Otto Richard Gottlieb (1920-2011), founder of the Laboratory of Natural Product Chemistry (IQUSP).

 “I follow the teachings of Professor Gottlieb, who always held that we should study and understand nature—a task that to him was even more important than describing a biological activity from the point of view of finding an application for human beings. Going back to follow Professor Gottlieb’s understanding is something that motivated me greatly,” he affirmed.
 
Kato has worked in bioprospecting projects with resources from BIOProspecTA, but his affinity for more academic work together with the difficulties in obtaining licenses for collecting biological material in Brazil ended up bringing about a change in career direction.

“About four years ago, I had a problem with some material we collected in Belém and was fined by Ibama [The Brazilian Institute of Environment and Renewable Natural Resources]. After that, I decided to do what I really wanted to do, which is to study the evolution and performance of metabolites for the organisms that produce them. I submitted the Thematic Project proposal and was delighted to be able to carry on Professor Gottlieb’s legacy,” he said.

Kato, who has been working with piperaceae for over 10 years, kept research alive in Block 11 of IQUSP, the traditional address of the lab founded by Gottlieb. The Piperaceae are near to the Myristicaceae and Lauraceae – all families that Gottlieb worked with. These plants produce substances the professor called neolignans, whose biosyntheses are still unknown.

“This is one of the things that made me start studying biosynthesis. I had to find a good working model and started with Miristicaceae, but I soon found it to be difficult. I needed to have material that could be easily propagated. Piperaceae are very good in this sense, because they produce many seeds in great quantities and grow quickly. All this facilitated the choice of the family as a model for the work,” he explained.
 
Phylogenetic tree

The Thematic project involves some 25 researchers spread throughout the country in addition to collaborators in Colombia. The team at the IQUSP Laboratory of Natural Product Chemistry includes seven doctoral students (five scientific initiation students and three post-doctorate students) aside from Kato as docent.
 
The methodology is based on field data collection. The group today has 1,500 accesses—each access being one collection made by an individual—nearly 150 species identified and some 100 species being cultivated in the IQUSP nursery.
 
“It’s a constant fight to keep them alive. Today, we make a copy of each of the species we have and try to send them to the Agronomical Institute [of Campinas] where they also keep a germplasm databank,” he explained.

According to Kato, the team uses biological markers in an attempt to organize the assemblage of species. He says the molecular markers help to define the phylogenic relationships and kinship between the species.

The first phase of the work is to define a phylogenetic tree. Then, the scientists will study the chemical composition of the groups in order to see whether the molecular phylogeny data correspond with the composition of secondary metabolites or not.
 
 “Once we have achieved this organization—and we have made reasonable progress in that direction—it will allow us to choose blocks of species to perform biosynthesis studies. In other words, to define which specie is the best for understanding the formation of a certain substance,” said Kato.

Biosynthesis consists of a series of phases of reactions in the formation of the substances. Knowledge of a synthetic pathway is important for beginning to define what the function of a certain substance is—a very difficult question to answer.
 
 “One thing is to try to take advantage of the substances for our own well-being (in the production of aromas or medications, for example) and another is to define the function of a substance for the plant. It’s a question we can’t answer immediately, but we can describe how the plant produces the substance and the sequence of reactions that lead to its production,” said Kato.

The study of biosynthesis seeks to discover what the precursor of each substance is, what its intermediaries are, which enzymes are involved and what the final product is. “That is the description of the synthetic pathway. We can yet describe how this pathway is regulated and which factor stimulates production of the substance. This could be development, the temperature, the season, the amount of daylight, and so on,” he affirmed.

In determining what affects production of the substance, scientists have a greater chance of understanding the function of the substance in the plant. The focus is not applications but, if the plant has an active principle, an already known biological application or activity, when the factors that regulate its production are discovered, researchers can optimize it in the field.

 “In two cases, we saw that the highest production levels of one metabolite occurred at dawn. As the growth is controlled, we could tell that increased production was related to some stimulus related to light. The idea in our project is to cultivate plants and submit them to a number of different situations, varying the stimuli,” he said.

The project is fundamentally multidisciplinary. “The students have an excellent opportunity to work on a very broad topic and with researchers from other areas. But we still have a great need to aggregate researchers from more fields such as biotechnology, for example,” declared Kato.