Design and generation of hormone receptor microProteins for ethylene, cytokinin and gibberellin

Abstract

MicroProteins are small, separately expressed parts of a larger protein and able to interfere with the full-length protein’s function. To enable modulation of hormone perception, microProteins were designed from the ethylene, cytokinin and gibberellin receptors. The protein isoforms designed to function as microProteins were overexpressed in Arabidopsis. Overexpression of a shortened gibberellin receptor GID1b isoform seems likely to lead to delayed stem growth and flowering. The isoform likely stabilizes DELLA proteins by protecting them from proteasomal degradation whilst not interfering with their suppression of gibberellin responsive genes. This work indicates that microProteins can be readily designed to influence hormone signaling in plants.

Popular Abstract

Hormone therapy for plants?

Just like humans, plants have hormones. These hormones influence plant growth, and how their organs develop. What if we could give plants a form of hormone therapy to change how they grow, and improve their traits?

Plant hormones are critical for how a plant develops and what it ends up looking like. Having more or less of a certain hormone can cause leaves to grow or die off, roots to lengthen, fruits to ripen, seeds to germinate, flowers to form, and so on. Because of the importance of plant hormones, plant breeders might want to influence how sensitive plants are to these hormones. By changing how a plant perceives hormones, important traits of crops can be altered. For example, we could stop leaves from dying off, or fruits from becoming overripe.

Changing sensitivity to hormones
Plants use specific proteins to sense their own hormones and shape their growth. Often, these proteins only work if they work together: two equal parts make one working sensor. However, if we make the plants also build smaller variants of the proteins involved, called microProteins, we can derail the process. Instead of two normal proteins, there are then also combinations of normal proteins and microProteins, which do not work properly. This changes how the plant senses the levels of its hormones. Specifically, we changed how plants sense the amount of a hormone called ‘gibberellin’ in their cells. We found that we can make plants think that they have less gibberellin than they actually do. Plants have a certain protein that makes sure the plants do not grow too quickly when there is no gibberellin. When the plant makes gibberellin, this protein gets destroyed. Our microProtein version of the protein that senses gibberellin is actually able to prevent this destruction, meaning that even when there is gibberellin the plants do not act like it. When making this microProtein our plants became very slow growers and did not make stems and flowers, while the normal plants did. This reduced growth we saw in our plants, means that plants with this microProtein do not grow as high as they otherwise would, which could for example make them easier to harvest. Because gibberellin is also involved in flowering, cabbage or lettuce plants making our microProtein would think they have less gibberellin and can thus be kept from flowering.

Why give plants hormone therapy?
Biotechnologists can use this technology of making microProtein versions of normal proteins in their work to improve plants. If they find out that the trait they want to change is influenced by hormones, they can try to change how the plant perceives its hormones using microProteins. It could even be possible to do this in specific parts of the plant, or at specific times. Most fruits ripen because the plant makes a hormone called ‘ethylene’ and perceives it in the fruit. Maybe the breeders want to make sure the fruits do not become overripe? Then they can get the plant to make a microProtein version of the proteins they use to perceive the hormone ethylene. This would make the plants feel like there is less ethylene than there actually is and stop the ripening. By having the plant make these microProteins only when the fruits have already ripened enough, plant breeders could stop fruits from overripening. In this way, hormone therapy for plants can help us grow better crops.

Master’s Degree Project in Biology 60 credits 2021
Department of Biology, Lund University

Advisor: Dr. Stephan Wenkel
Associate Professor, Section for Plant Biochemistry, University of Copenhagen

• author: Muthert, Lucius
• supervisor: Stephan Wenkel
• organization: Degree Projects in Biology
• course: BION03 20202
• year: 2021
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9063645
• date added to LUP: 2021-08-24 12:05:36
• date last changed: 2021-08-24 12:05:36