Researchers from the University of Cordoba, in Spain, for the first time, identified the genetic mechanisms that enable microalgae to produce auxin, a plant hormone that plays a crucial role in chemical communication and symbiotic relationship with bacteria. This discovery opens up exciting possibilities for harnessing these interactions to develop sustainable algae-based bio stimulants for agriculture.
Auxin, renowned for regulating plant growth and orchestrating processes like root and leaf development, also plays a pivotal role in algae -described by the research team as “the plants’ cousins’”. While it has long been known that algae produce auxin, the molecular process behind this remained a mystery until now.
The study, led by researchers Victoria Calatrava and Aurora Galván alongside Ángel Llamas and Emilio Fernández, reveals that the model alga Chlamydomonas reinhardtii produces auxin through an enzyme known as L-amino acid oxidase (LAO1). “The pathway for auxin production that we demonstrate here is very simple and widespread. It involves the enzyme L-amino acid oxidase (LAO1), which produces auxin using tryptophan,”, explains Galván.
The process takes place in the periplasmic space of the alga, a kind of permeable membrane where the enzyme is located. According to the researchers, this enables auxin to be released externally for communication with other organisms or utilised internally to regulate the algae’s metabolism.
Symbiosis with bacteria and agricultural applications
The team also found that this hormone not only regulates algae growth but facilitates a mutualistic relationship with bacteria of the genus Methylobacterium. “The accumulation of auxin is harmful because it slows growth. At low concentrations, it enhances algae growth, but in excess, it inhibits it,” explains Calatrava. This is where the bacteria come into play: they degrade the excess auxin, enabling the algae to keep growing. In return, the bacteria feed on the auxin.
This symbiotic relationship has significant agricultural implications. Both algae and bacteria are part of the microbiota plant, and their interaction could be key to promoting crop growth and improving resilience to environmental stresses such as drought. “The production and regulation of auxin could enhance agricultural output, boosting growth while improving tolerance to stresses like drought,” highlights the study.
A step towards sustainable farming
The researchers emphasise the potential of this discovery to create bio-stimulants based on algae-bacteria-plant interactions. These products could become invaluable tools for a more environmentally friendly approach to farming.
The study not only deepens understanding of algae’s role in agricultura ecosystems but also underscores their ability to influence plant microbiota and foster beneficial symbiosis. “We are now looking to understand how these interactions can be applied to develop bio-stimulants for sustainable agricultural production,” the authors conclude.
Published in the scientific journal iScience, this groundbreaking research represent a milestone in agricultural biotechnology and opens up new opportunities to integrate natural processes into improving crop productivity.
Reference:
Calatrava V, Hom EFY, Guan Q, Llamas A, Fernández E, Galván A. Genetic evidence for algal auxin production in Chlamydomonas and its role in algal-bacterial mutualism. iScience. 2023 Dec 16;27(1):108762. doi: 10.1016/j.isci.2023.108762
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