March 3, 2021

Solved the mystery of the plant that doubles in size in a day

The tiny aquatic plant Wolffia.

The tiny aquatic plant Wolffia.
Sowjanya Sree / Philomena Chu

New findings on the genome of the tiny duckweed, whose scientific name is Wolffia, explain how it is able to grow so fast, at an unbeatable pace in the nature.

Wolffia, what grows in fresh water on all continents except the Antarctica, looks like little floating green seeds, with each plant the size of the head of a pin. It has no roots and only a fused stem-leaf structure called a frond. It reproduces in a similar way to yeast, when a daughter plant sprouts from the mother. With a doubling time of just one day, some experts believe that Wolffia could become a major source of protein to feed Earth’s growing population. (It is already eaten in parts of Southeast Asia, where it is known as khai-nam, which translates to “water eggs.”)

To understand which adaptations in the Wolffia genome account for its rapid growth, researchers led by scientists from the Salk Institute grew the plants in light / dark cycles And then they analyzed them to determine which genes were active at different times of the day. (The growth of most plants is regulated by the light-dark cycle, with most growth taking place in the morning.)

“Surprisingly, Wolffia only has half the number of genes regulated by light / dark cycles compared to other plants“says Todd Michael first author of the paper and research professor at Salk’s Laboratory of Cellular and Plant Molecular Biology at Salk.” We think that’s why it grows so fast. It doesn’t have the regulations that limit when it can grow. ”

The researchers also found that genes associated with other important elements of plant behavior, such as defense mechanisms and root growth, are not present. “This plant has lost most of the genes it doesn’t need,” adds Michael. “It seems to have evolved to focus solely on rapid and uncontrolled growth.”

“Data on the Wolffia genome can provide important information on the interaction between how plants develop their body plan and how they grow“says HHMI researcher and professor Joseph Ecker, who is also director of the Salk Genomic Analysis Laboratory and a co-author of the paper.” This plant promises to become a new laboratory model for studying the central characteristics of plant behavior, including how genes contribute to different biological activities. ”

One of the goals of Michael’s lab is to learn how to develop new plants from scratch so that they can be optimized for certain behaviors. The current study expands the knowledge of basic plant biology and offers the potential to improve crops and agriculture. To the make plants better able to store carbon from the atmosphere in their roots, an approach pioneered by the Salk Plant Harvesting Initiative, scientists can optimize plants to help address the threat of climate change.


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