How Plants Obtain Nitrogen by Supplying Iron to Symbiotic Bacteria

IMA peptides in legumes enhance iron acquisition for nitrogen fixation, offering insights into sustainable agriculture practices.

Leguminous plants have a mechanism (rhizobial symbiosis) to efficiently acquire nitrogen, which is an essential macronutrient for growth, through the nitrogen-fixing bacteria rhizobia. Root nodules are organs on plant roots that facilitate the symbiotic relationship. Rhizobia colonizes these nodules and fix nitrogen by converting nitrogen from air into ammonia. Iron is needed for the enzymes that catalyze nitrogen fixation; however, where and how iron is transported to the nodule and used for nitrogen fixation is largely unknown.

Discovering the Role of IMA Peptides

In this study, using the legume model plant Lotus japonicus, a transcriptome analysis was performed based on the nitrogen status in the plant body during the rhizobial symbiosis process. IRON MAN (IMA) peptides consisting of approximately 50 amino acids<div class="cell text-container large-6 small-order-0 large-order-1">
<div class="text-wrapper"><br />Amino acids are a set of organic compounds used to build proteins. There are about 500 naturally occurring known amino acids, though only 20 appear in the genetic code. Proteins consist of one or more chains of amino acids called polypeptides. The sequence of the amino acid chain causes the polypeptide to fold into a shape that is biologically active. The amino acid sequences of proteins are encoded in the genes. Nine proteinogenic amino acids are called "essential" for humans because they cannot be produced from other compounds by the human body and so must be taken in as food.<br /></div>
</div>” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>amino acids were identified, which function systemically (shoot and root systems) to collect iron into the nodules following rhizobial infection.

Insights from Comparative Analysis

Furthermore, the function of IMA peptides was analyzed in L. japonicus and Arabidopsis thaliana, a plant devoid of rhizobial symbiosis. In both plant speciesA species is a group of living organisms that share a set of common characteristics and are able to breed and produce fertile offspring. The concept of a species is important in biology as it is used to classify and organize the diversity of life. There are different ways to define a species, but the most widely accepted one is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable offspring in nature. This definition is widely used in evolutionary biology and ecology to identify and classify living organisms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>species, the IMA peptides maintained nitrogen homeostasis by obtaining iron in response to increased nitrogen concentrations in the plant body, thereby regulating plant growth.

The research group previously identified a mechanism for regulating rhizobial symbiosis in response to the presence of nitrogen in the soil. This study builds on previous studies by clarifying the underlying mechanism of iron acquisition in response to nitrogen, which provides further insight into the mechanisms of plant adaptation to the environment.

Contributions to Sustainable Agricultural Practices

These findings are promising for the development of new technologies that contribute to a sustainable society by maximizing the capacity of plants for microbial symbiosis in terms of nutrient use.

Reference: “IMA peptides regulate root nodulation and nitrogen homeostasis by providing iron according to internal nitrogen status” by Momoyo Ito, Yuri Tajima, Mari Ogawa-Ohnishi, Hanna Nishida, Shohei Nosaki, Momona Noda, Naoyuki Sotta, Kensuke Kawade, Takehiro Kamiya, Toru Fujiwara, Yoshikatsu Matsubayashi and Takuya Suzaki, 29 January 2024, Nature Communications<em>Nature Communications</em> is a peer-reviewed, open-access, multidisciplinary, scientific journal published by Nature Portfolio. It covers the natural sciences, including physics, biology, chemistry, medicine, and earth sciences. It began publishing in 2010 and has editorial offices in London, Berlin, New York City, and Shanghai. ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Nature Communications.
DOI: 10.1038/s41467-024-44865-4

This research was supported by Ministry of Education, Culture, Sports, Science and Technology KAKENHI grants (JP20H05908 and JP23H02495 to T.S.); JSTMirai Program (JPMJMI20E4) to T.S.