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The summer of 2021/22 was one of the wettest Australia has seen in years. Extremely humid, and too much rain spoiling our fun in the sun. But the Australian people rejoiced, “Hooray! Thank goodness”,
the bushfires this year were not as extreme as the Black Summer a few years ago that emaciated the countryside. No, instead another devastating event reigned, the rise in cereal rust infections decimating
our wheat and grain crops and spreading rapidly across farmlands. But how were we to know when such instances are hardly as reported as the bushfires? Truly, raise your hand if you have heard about cereal
rusts at any point in your life.
Fast forward a few weeks, where this year’s UNSW iGEM team were grocery shopping for snacks, preparing to double-down on a study session in an effort to begin our iGEM journey by selecting a topic to investigate.
“That’s strange,” one of our team members thought, baffled by the rise in prices of the biscuit and bread and pastry products we were about to purchase. Oddly higher than usual. We thought nothing of it, of course,
what’s a few extra dollars we have to pay? Chump change. But the more we thought about it, the more we realised, what if we weren’t able to afford these products? What if we or our families were dependent on this
food for dinner and we couldn’t buy it?
Cereals and grains like wheat and barley form a quintessential component of our everyday lives, without us giving them second thought as to how they got on our plate. It is an intensive and arduous process
cultivating such a crop, especially given the weight of importance it holds in both a social aspect and an economic sense. In fact, Australia generates 25 million tonnes of wheat per year, accounting for 3.5%
of the global wheat production, and is expected to continue rising to producing around 32 million tonnes in the next year (Australian Export Grains Innovation Centre, 2022). When this dynamic is thrown off course,
like with the emergence of dangerous plant diseases like cereal rust, it presents serious problems for a fragile economy and a starving planet.
Our team was inspired by the resilience of the thousands of farmers across Australia in the face of adversity. Standing on the shoulders of the decades’ worth of hard work put in by biologists, agriculturists
and many others, we wanted to continue contributing to the growing body of efforts put forth to maintain a sustainable and fruitful agricultural industry. Here, the calamitous and fraught, cereal rust, threatens
to undo this great work. And so, our team were called to action to investigate such an enigmatic and problematic issue, one that, although has been known for over a hundred years in Australia, is still far from
reaching a resolution. In doing so, we were, and still are, extremely intrigued by the role synthetic biology has to play in assuaging the impacts of cereal rust and focused on applying the tools in the synthetic
biology toolkit to accomplish such a feat as preserving the future of wheat agriculture for the next generations.
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As an infectious plant disease, the obvious cause of cereal rust is clear, the pathogenic fungus Puccinia spp. (Agriculture Victoria, 2022). This spore-forming fungus possesses a complex reproductive cycle,
where once it attaches to the wheat plant, it releases a myriad of virulence effector proteins involved in enhancing the pathogenesis, invasion and dissemination. In doing so, the wheat host significant damages,
leading to reddish-orange stains on the stem and producing a shrivelled grain.
Though this may seem clear-cut, the broader social and ecological landscape surrounding the cause of cereal rust is much more intricate and sophisticated. Wet, moist conditions provided by a changing climate due
to human intervention supports a breeding ground for Puccinia spp., significantly increasing the incidence and spread across large distances. Similarly, the overuse and misuse of the conventional chemical fungicides
have resulted in the emergence of newer, more deadly and resistant strains of the fungus, such that these traditional approaches prove ineffective. These exacerbating factors work to only heighten the problem for
the future.
As such, the wide-reaching impacts of cereal rust are too great to ignore, involving: (1) a significant blow to the grains agricultural industry, with a domino effect observed in industries reliant on wheat;
(2) a threat to the livelihood of the thousands of grain farmers in Australia and the many more globally; (3) a national shortage of foods posing a dangerous risk to those most susceptible to experience this
food insecurity; and (4) a potential risk to the health of the public through the emergence of other pathogenic microorganisms in the soil of the wheat ecosystem.
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Thus far, all that has been done in attempting to treat cereal rust is equivalent to sticking a flimsy Band-Aid on a gushing wound. Clearly, there is not a “one size fits all” approach for this problem. So, a
solution specific to cereal rust is greatly needed. This is where synthetic biology comes in. Here, to solve a problem this grand, we need a solution just as grand and innovative in size. Synthetic biology offers
a novel, limitless avenue to engineer biological systems in order to create new functions. Its benefits have already been realised in fields relating to medicine, environmental sciences and even agriculture. So
why not here and why not now?
Our team knows that synthetic biology is not always the cure, though, alongside a holistic approach utilising other cereal rust control measures, it still holds useful applications. Our project is only one example
where this is highlighted, exploiting the design, building and testing of genetically modified material to eradicate cereal rust, root-and-stem.
This year, our team has developed a considerate solution to inhibit the growth of Puccinia spp. through the design of novel peptide candidates targeting vital effector proteins involved in the fungal pathogenesis.
In particular, our team chose to focus on investigating the PstSCR1 and Pst_12806 effectors, seeing as the literature attribute quite severe disease phenotypes with the presence of these proteins. PstSCR1 is known
to be involved in suppressing the host immunity of the plant while also mediating nutrient uptake into the fungus to support its parasitism (Dagvadorj et al., 2017). Similarly, Pst_12806 is upregulated during
infection and is shown to impair the functioning of photosynthesis in the chloroplast of the plant cell as well as reducing the accumulation to antimicrobial reactive oxygen species as a means to support the fungus’
growth and development (Xu et al., 2019).
In studying how these effector proteins interact with the host proteins, namely PstSCR1 with the plant immune signalling receptor SERK3B and Pst_12806 with a component of the photosystem called TaISP, we were able
to computationally design and model a collection of peptide candidates based on these interactions (Dagvadorj et al., 2017; Xu et al., 2019). Here, these peptides should, in theory, bind with higher affinity to the
fungal target proteins in order to inhibit their involvement in the fungal growth and invasion.
Though we are still in the early stages of designing such a complex solution to a delicate issue, we have also planned to incorporate sequences encoding these peptides in a bacterial vector with an integrated MazEF
antitoxin/toxin kill switch to control the survival of this genetically modified organism and ensure it remains within its site of application.
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Human Practices
Our team knows that there is a stark disconnect between science and society. As such, our human practices team aimed to resolve this obstacle.
The overarching aim of our human practices team was to meaningfully engage with key user groups affected by cereal rust to gain a more resolved
and complete picture of the extent of the issue. In understanding and empathising, only then can we truly begin to know how to approach the issue.
By coordinating with a range of these stakeholders, including traditional land owners, governments, agricultural businesses and a selection of
academics from various disciplines, were we able to integrate their voices and guidance into every step of our project, from the ideation and design
step to the implementation and communication of our solution. In the hopes to facilitate a clear stream of communication, we vowed to inform our
stakeholders of our progress and valued their opinions on the possible role synthetic biology has in their lives. In the future, we encourage the
continuation of our beautiful and meaningful relationships between our team, the innovators attempting to alleviate the burden of cereal rust, and the
stakeholders, real people with real lives on the line that are impacted by the problem and our solution.
Dry Lab
With investigating a topic so wildly understudied and limited experimentations performed in the past, our dry lab team was integral in uncovering the
predicted structure and functioning of the components of our solution. Here, our dry lab team aimed to discover a list of potential targets from the far
from annotated genome of the Puccinia fungus. Subsequently, they were key in modelling the structure of the fungal target proteins and their binding
affinity to a collection of peptide candidate sequences. In performing something as radical as synthesising peptides from very little information, we
hope this process may be applicable beyond the scope of this project and extended to computationally studying the protein biology of other
understudied yet noteworthy plant diseases.
Wet Lab
Though our dry lab team provided substantial help in studying the interaction of the fungal target proteins and our designed peptides, this does not
correlate to actual binding. As such, our wet lab team aimed to test in vitro the binding affinity of these protein-protein interactions. By transforming
and expressing both the fungal proteins and the peptides in E. coli cells and performing Förster resonant energy transfer (FRET) assays to measure molecular
interactions, our team would be able to prove, or disprove, the results generated by our dry lab team. This is a vital aspect to synthetic biology,
relating to the design-build-test paradigm central to the scientific methodology. Furthermore, our wet lab team aimed to consider the safety concerns
associated with the implementation of such a solution, and so designed a biocontainment system to be used when applying our solution to its target site.
This is yet to be tested, but will be a focus for the future of our project.
Education and Communication
Science education and communication is key in facilitating the relationships between researchers and the wider public. Here, our education and communication
team were tasked with raising awareness of cereal rust as a growing problem that has implications for the community. Shockingly, at the beginning of our project,
when we asked the public if they knew of cereal rust, the most common answer related to the rusting that occurs on metallic structures. Yet, by the end of our
iGEM journey, it appears we have successfully brought to people’s attention this typically dismissed plant disease. Not only did we want to raise this issue with
the public, but we wanted to educate the next generation about the potential for synthetic biology as a potential avenue to pursue in treating the cause of this
problem. Thankfully, our communication with the next generation proved fruitful and piqued their interest in contributing to solving other big world issues beyond
cereal rust using synthetic biology as an important tool.
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