Professor Daniel Chitwood, Ph.D., and his group at the Donald Danforth Research Center in St. Louis, in collaboration with the University of California, Davis, are using an aquatic alga called Caulerpa taxifolia to study the nature of plant structure and form. Researchers from the University of Pennsylvania published their results in the online journal PLOS Genetics recently.

In Chitwood’s words, caulerpa is an organism like no other. This algae belongs to the green algae family, which is a plant family. Amazingly, it can reach a length of six to twelve inches from a single cell. The organs of land plants were uniquely adapted to it by independent evolution. In a developing cell, there is a stolon that extends downward along its surface, and from the stolon emerge leaf-like fronds and axial holdfasts that anchor the cell and absorb phosphorus. It is nothing more than one cell in all of these structures.” “For many years, I have been fascinated with the structure and form of plants, especially tomato. It is the land plant who has fascinated me more than anything else.” Detecting the factors determining structure and form in a complex tomato plant is a challenging task, as you might expect. The goal of better understanding plant growth and development is to provide more tools to create better plants and to ensure a more reliable food supply. The multicellularity of plants is an essential prerequisite for complex architectural structures. However, Caulerpa is also a plant, and it has evolved an independent body plan with a land plant-like body shape, but without multicellularity. In an explanation of how this happens, Chitwood and his team suggested that the structure of Caulerpa might be reflected in the RNA within In general, RNA’s are the products that are produced when genes are expressed or “turned on.” For example, near the frond part of the cell, RNA’s are different than near the holdfast part. The caulerpa analysis will also be able to provide insight into the distribution of RNA within cell nuclei, a feat that is often impossible because of the small, cellular structure of multicellular organisms. “What I had hoped for turned out to be even more interesting than I had imagined,” Chitwood said. It is not only true that different parts of the Caulerpa cell display distinctive RNAs, but there seems to be a correlation between RNAs that are expressed together in different parts of the Caulerpa cell and those expressed together in the multicellular organs of the The lineage that Caulerpa belongs to probably separated from the one giving rise to land plants more than 500 million years ago, but in many ways Caulerpa shares the same pattern of RNA accumulation as land plants do

As Chitwood continued, “our work on Caulerpa has been a complete paradigm shift for me and my team in our thinking about plant structure and development.” In addition to arising with and without multicellularity, the basic form associated with land plants is visible. The higher plant cells are connected to each other via channels known as plasmodesmata, and it has been argued that multicellular land plants are similar to organisms with single cells such as How would it be if we were able to see higher plants, like tomato, as a single cell instead of a bunch of cells? We find that multicellular land plants, like tomato, and giant single-celled algae, like Caulerpa, accumulate RNA in a similar way based on our study, which shows a shared pattern of RNA accumulation in both. We are far from the only researchers who have had to think about plant structure from a different perspective, but we believe that the most interesting outcome is that we have changed the way we think about it.”