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Robert Augustine and Small Ubiquitin-like Modifier (SUMO)

Over the past few decades, the world has experienced a rise in global temperatures, which has led to heat waves, heavy rainfall, droughts, and other changes. A more extreme result of climatic changes is an increase in the unpredictability of our environmental phenomena, which can have a large impact on crop yields around the globe. For this reason, climate change is one of the primary drivers of global hunger today, with reports from the World Food Programme citing that the past decade has seen upwards of 1.7 billion people affected by weather and climate-related disasters. 

Although many methods of combating food insecurity have been proposed, some proposed mechanisms, like expanding agricultural acreage, also bring about deforestation, which further increases global temperatures. The issue of climate change and agriculture thus becomes an issue of managing resources within a finite amount of land. 

One way to circumvent this challenge is to improve the efficiency of farmland, which brings us to the topic of today’s column, namely, how scientists are studying the way plants respond to environmental stress in order to genetically engineer crops able to withstand the ever-changing weather conditions. 

One of these scientists, Dr. Robert Augustine, works as the College’s new plant molecular cell and biochemical researcher and professor. I had the chance to speak with Augustine about his work in this field. He explained that plants are constantly pummeled by stresses like changes in temperature, UV exposure, and much more. In order to survive, plants have developed complex molecular defense mechanisms such as the protein SUMO (Small Ubiquitin-like Modifier). SUMO is a small protein that attaches itself (SUMOylates) to other proteins in order to modify their development and respond to environmental stress. Upon binding, there are many possible outcomes. In fact, one way to think of SUMO is as a great cellular multitasker capable of causing or protecting against protein degradation, promoting or breaking protein/protein interactions, changing localization of proteins, or changing enzymatic function. Overall, these attributes lend to the complexity of SUMO. 

Understanding SUMO’s ability to cause a variety of outcomes also has important implications in changing the way plant-stress research is currently carried out. Typically plant researchers are interested in one type of stress. SUMO, however, plays a key role in responding to a wide array of stresses like irregular salt intake, UV protection, drought, nutrient limitations, and heat. As a result, SUMO is versatile and an important protein to study as understanding the pathways involved can allow scientists to genetically engineer plants capable of responding to multiple environmental conditions. 

This versatility does make studying SUMOylation tricky, however. Most of the 1500 different proteins that SUMO modifies are within the nucleus, so it is no wonder that designing experiments to tease out these pathways is a lengthy undertaking. Furthermore, the proteins being SUMOylated within the nucleus indicate that changes being made are linked to gene expression and RNA splicing. The approaches Dr. Augustine takes are primarily genetic, meaning he knocks out genes that are involved in attaching SUMO to its targets and studies the effects on the plant in order to understand how the SUMOylated proteins impact plant function. 

The way Dr. Augustine studies SUMO has also changed over the years. His research began in corn plants, but he has since transitioned to using moss as a model organism. A few advantages to working with moss, he explained, include its ability to be grown in smaller spaces and at a fast rate. Further, moss has a few genetic tricks such as its haploid cells that eliminate the need for knocking out two copies of the same gene. Additionally, moss has a simple lifecycle and has very thin cell walls, making it easy to image under a microscope. Finally, moss has the ability to regrow an entire plant from a single cell. If you cut the leafy-gametophore and isolate it on a petri dish, the leaf will revert into a stemcell state and eventually become filamentous cells again.

This is further evidence of the ease with which they are able to rewire their genomes – making it a good model for looking at questions of transdifferentiation. Although a complete connection has yet to be established, Dr. Augustine explained that transdifferentiation in moss cells may be similar to the way SUMO binds to many proteins and, according to the current hypothesis, acts as a way the plants can rewire their genomes in times of stress and possibly act as an on/off master switch for gene expression. 

In moss the process of differentiating cells in their stemcell states is akin to rewiring the genome. One area of further study, however, comes in when translating between moss and flowering plants or agricultural crops, although basic concepts are likely to be shared between the two.

Another interesting feature of SUMO is that unlike most proteins which denature upon heating, SUMO can withstand incredibly high temperatures. Although the reason behind SUMO’s high thermostability is not fully understood, it may play a role in SUMO’s ability to protect plants against heat stress.

Dr. Augustine’s research centers around identifying the mechanism behind SUMOylation. The current hypothesis in his lab is that SUMO rewires the genome to turn on or change gene expression, which leads to its ability to turn on defenses and turn off genes that are unnecessary for survival. As issues of food scarcity increase, this research is incredibly important for our collective well-being in the future. 


 ~ Victoria Melehov `25

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