Two University of Wisconsin researchers Edgar Spalding and Takeshi Yoshihara recently published a study concluding that there are two ways for plants to monitor the direction of gravity — a sensing machine like humans do and a mutation of the LAZY and SLQ1 genes.
Previously, the only way for plants to know which direction was up was through the cellular body settling to the bottom of certain cells, according Spalding — who is also a professor emeritus in the botany department.
“[Humans] have something in [their] inner ear that tells us our orientation,” Spalding said. “Plants have something like that. They have a little detector in them. A cellular body that settles down to the lowest side of certain cells.”
The study looks at five LAZY genes in a common plant that is used for research called Arabidopsis, according to Spalding. Without the LAZY genes, all Arabidopsis plants fail to grow straight up and down, according to Spalding.
But, Yoshihara discovered one plant in the experiment that was still standing after all the LAZY genes got knocked out of the DNA sequence by the researchers. After sequencing this plant, the SLQ1 gene was discovered to be broken, according to Spalding.
“[The breakage] is a change in the DNA sequence,” Spalding. “In this particular case, only one letter change in the DNA caused the plant to stand up.”
This change was due to a suppressed mutation that corrects another mutation occurring in the gene sequence of an organism, according to Spalding.
Deciphering which mutation occurred to make the plant stand up despite the lack of LAZY genes required a lot of DNA sequencing and analysis of the sequencing, according to Spalding. The Arabidopsis has around 23,000 genes, about the same amount as humans, and the protein change that supports the plant is caused by a single gene, the SLQ1 gene, according to Spalding.
“One of the amino acids was changed in the protein which caused the plant instead of growing down and flopping on the soil to stand upright,” Spalding said.
Future implications of the study can help with crop efficiency and optimization to provide humans with more food, according to Spalding.
To create crops that can grow closer to each other, crops must have more vertical angles of their branching, according to Spalding. When the shoot of the plant is more vertical it can be packed into a field and also have increased nutrient pickup in its roots, Spalding said.
“Steering roots stepped by adjusting the angles they’re trying to grow to may be more effective in getting the required water in an agricultural setting,” Spalding said.
Utilizing this research allows for scientists to have a better idea on how plants have evolved since they migrated to terrestrial environments to support life on earth, Spalding said.
