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Borrowed gene helps maize adapt to high elevations, cold temperatures


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Researchers at North Carolina State University show that an important gene in maize called HPC1 modulates certain chemical processes that contribute to flowering time and has its origin in “teosinte mexicana,” a precursor to modern-day maize that grows wild in the highlands of Mexico. The findings provide insight into plant evolution and trait selection, and may have implications for the adaptation of maize and other crops to low temperatures.

“We are generally interested in understanding how natural variation of lipids is involved in plant growth and development, and how these compounds can help plants adapt to their immediate environment,” said Rubén Rellán-Álvarez, assistant professor professor of structural and molecular biochemistry at NC State and the corresponding author of a paper describing the research. “In particular, we wanted to learn more about variation in lipids, called phospholipids, which consist of phosphorus and fatty acids, and their role in adaptation to cold, low phosphorus and the regulation of important processes for plant fitness and yield, such as flowering time. “

Corn grown at higher elevations, such as the highlands of Mexico, needs special accommodation to grow successfully. The colder temperatures in these mountainous regions put corn at a slight disadvantage compared to corn grown at lower elevations and higher temperatures.

“At high altitudes, in colder temperatures, it takes longer to make a corn plant because of the lower accumulation of heat units — corn needs to accumulate heat or growth units,” Rellán-Álvarez said. “At 2,600 meters altitude, it takes three times longer to make a corn plant than at lower altitudes. To adapt to these special conditions, campesinos – smallholders – have to plant early in the season and plant deep in the ground. is very slow but steady growth in the early months until the rainy season arrives. Over the millennia, campesinos have selected maize varieties that can thrive in these special conditions by being able to grow in low temperatures and bloom early before the colder months come into winter .”

That’s where the HPC1 gene comes in, the researchers say. In low-altitude corn varieties, including most corn grown in the United States, the gene breaks down phospholipids that have been shown in other species to bind to key proteins that speed up flowering time.

“Phospholipids are also important building blocks of cell membranes. All lipids have different shapes, and balancing these shapes keeps membranes intact and helps plants survive periods of stress,” said Allison Barnes, a postdoctoral researcher in Rellán’s lab. Álvarez and co-first author of the article.

In the mountains, however, the gene does not work, but in favor of highland maize.

“In highland maize, a defective version of the gene was selected and this led to high levels of phospholipids,” Rellán-Álvarez said. “We developed a CRISPR-Cas9 mutant and confirmed the metabolic function of the gene. We also showed similar phospholipid-protein interactions described in other species to regulate flowering time.”

“The phospholipids that don’t break down in the highlands may be better at holding the membranes together so the plant can survive the adverse environment,” Barnes added.

In the paper, the researchers show the results of extensive experiments across Mexico — in lowlands and highlands — in which the highland version of the gene was present. They found that corn with the highland version of the gene flowered a day earlier than plants without that version of the gene. Meanwhile, in the lowlands, corn with the highland version of the gene bloomed a day later than plants without that gene version.

“It helps the plant do better in its local environment,” said Fausto Rodríguez-Zapata, a Ph.D. student in Rellán-Álvarez’s lab and co-first author of the paper. “If flowering doesn’t work, there’s no seed, so it’s not surprising that something to do with flowering time is also involved in local adaptation.”

The study also examined the evolution of maize through thousands of years of farmer selection in the Western Hemisphere. Thousands of years ago, Native Americans domesticated maize in southwestern Mexico from a wild plant called teosinte parviglumis, and with great ingenuity they brought and adapted maize across America — from the deserts of Arizona and Peru to the humid forests of Yucatán and Colombia. , including to the Mexican highlands, where corn was crossed with another wild teosinte plant – teosinte mexicana.

“Our results show that the mixture of maize with teosinte mexicana helped the maize adapt to highland conditions and that this mixture is relevant in modern maize,” said Rellán-Álvarez.

In the study, the researchers showed that genetic pieces of teosinte mexicana — namely the highland version of HPC1 — are preserved in modern corn.

“This retention — what scientists call introgression — is similar to modern humans retaining bits of Neanderthal in their genetic code. These pieces are retained because they’ve been selected over time and provide some benefit,” Rodríguez-Zapata said.

The study also showed the highland variant of HPC1 in corn grown in Canada, the northern United States and northern Europe, which makes sense given the colder climate in those locations.

The NC State researchers are now investigating the role of these and other genes involved in phosphorus metabolism to learn more sustainable ways to grow corn and perhaps bring more teosinte mexicana into modern corn.

The paper appears in Proceedings of the National Academy of Sciences† Researchers from Penn State University, UC Davis, Iowa State University, Cornell University and Cold Spring Harbor co-authored the paper.

Genome sequencing shows maize adapted to the highlands thousands of years ago

More information:
Allison C. Barnes et al, An adaptive teosinte mexicana introgression modulates phosphatidylcholine levels and is associated with maize flowering time, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2100036119

Provided by North Carolina State University

Quote: Borrowed gene helps corn adapt to high elevations, cold temperatures (June 2022, June 30) retrieved June 30, 2022 from https://phys.org/news/2022-06-gene-maize-high-elevations-cold .html

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