University of Wisconsin-Madison researchers have discovered where an important photoreceptor acts within plant stems, and the finding could help growers improve the success rate of crops like soybeans.
Published in the journal Current Biology, the research brings new understanding to how seedlings detect light in their environment and inform their growth strategy.
Researchers have known that photoreceptors help seedlings detect when they have reached ample sunlight, when to stop elongating their stems and when to begin photosynthesis to produce energy. But until now, they weren't sure where in the seedling these photoreceptors acted and had to look at the entire plant to study the resulting phenomena.
"For the first time, we realized that the effect of these photoreceptors is not everywhere along the stem and that different photoreceptors control different regions of the stem," explains Edgar Spalding, a professor emeritus of botany at UW-Madison.
Spalding, along with doctoral student Julian Bustamante and data scientist Nathan Miller, isolated the effects of certain photoreceptors through genetic manipulation editing and photographed the growth of tiny sprouting seedlings with highly sensitive cameras. They analyzed the photos with machine learning and the UW's high-throughput computing resources to determine where each photoreceptor controlled growth on the stem. Stand establishment - the healthy early development of a plant taking root in soil - is a critical indicator for crop success. Understanding precisely how photoreceptors contribute to this vulnerable period of growth is of great interest to farmers and researchers alike.
To sprout, a plant elongates its stem to break through the soil until its photoreceptors detect enough sunlight that would allow the plant to generate its own energy through photosynthesis. Before then, it must rely on the limited cache of energy and nutrients stored in its seed.
Sometimes, after seedlings emerge from soil, they can be covered up again by dirt from wind, a foraging animal, or other factors. Without adequate exposure to sunlight, the photoreceptors signal to the plant that it can no longer make energy through photosynthesis. But thanks to a photoreceptor called cryptochrome-1 (cry1), that's not the end of the seedling.
Spalding and his team discovered that cry1 not only controls the elongation of the upper part of the plant stem, but it also plays a role in getting the plant back into the sunlight.
When a plant initially sprouts, cry1 stops the plant from fully elongating, saving some energy and stem length in reserve. That way, when a seedling is covered up again, this photoreceptor can signal the plant to elongate its stem until it's above soil once more.
Researchers could use this new knowledge to genetically alter seeds to enhance the role of cry1, ensuring vulnerable crops have the backup elongation length and energy they need to reemerge if covered again.
Spalding hopes this work will help focus future areas of crop innovation research and create more resilient plants that produce a more profitable yield.
