From University of New South Wales (AU) : “Mystery of photosynthetic algae evolution finally solved”

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From University of New South Wales (AU)

30 Mar 2021
Lachlan Gilbert

Scientists have identified the protein that was the missing evolutionary link between two ancient algae species – red algae and cryptophytes.

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A computer model of the novel protein structure in the cryptophyte’s antenna that traps sunlight energy. Credit: UNSW.

An evolutionary mystery that had eluded molecular biologists for decades may never have been solved if it weren’t for the COVID-19 pandemic.

“Being stuck at home was a blessing in disguise, as there were no experiments that could be done. We just had our computers and lots of time,” says Professor Paul Curmi, a structural biologist and molecular biophysicist with UNSW Sydney.

Prof. Curmi is referring to research published this month in Nature Communications that details the painstaking unravelling and reconstruction of a key protein in a single-celled, photosynthetic organism called a cryptophyte, a type of algae that evolved over a billion years ago.

Up until now, how cryptophytes acquired the proteins used to capture and funnel sunlight to be used by the cell had molecular biologists scratching their heads. They already knew that the protein was part of a sort of antenna that the organism used to convert sunlight into energy. They also knew that the cryptophyte had inherited some antenna components from its photosynthetic ancestors – red algae, and before that cyanobacteria, one of the earliest lifeforms on earth that are responsible for stromatolites [Trends in Microbiology].

An image of Cyanobacteria, Tolypothrix.

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Stromatolites at Shark Bay, Western Australia. Credit: Brendan Burns/ UNSW Sydney.

But how the protein structures fit together in the cryptophyte’s own, novel antenna structure remained a mystery – until Prof. Curmi, PhD student Harry Rathbone and colleagues from University of Queensland (AU) and University of British Columbia (CA) pored over the electron microscope images of the antenna protein from a progenitor red algal organism made public by Chinese researchers in March 2020 [Nature].

Unravelling the mystery meant the team could finally tell the story of how this protein had enabled these ancient single-celled organisms to thrive in the most inhospitable conditions – metres under water with very little direct sunlight to convert into energy.

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A cryogenic electron microscopy map of a cryptophyte-like protein found in red algae. The red indicates the elusive protein that was re-used by cryptophytes in their own antenna. Credit: UNSW.

Prof. Curmi says the major implications of the work are for evolutionary biology.

“We provide a direct link between two very different antenna systems and open the door for discovering exactly how one system evolved into a different system – where both appear to be very efficient in capturing light,” he says.

“Photosynthetic algae have many different antenna systems which have the property of being able to capture every available light photon and transferring it to a photosystem protein that converts the light energy to chemical energy.”

By working to understand the algal systems, the scientists hope to uncover the fundamental physical principles that underlie the exquisite photon efficiency of these photosynthetic systems. Prof. Curmi says these may one day have application in optical devices including solar energy systems.

Eating for two

To better appreciate the significance of the protein discovery, it helps to understand the very strange world of single-celled organisms which take the adage “you are what you eat” to a new level.

As study lead author, PhD student Harry Rathbone explains, when a single-celled organism swallows another, it can enter a relationship of endosymbiosis, where one organism lives inside the other and the two become inseparable.

“Often with algae, they’ll go and find some lunch – another alga – and they’ll decide not to digest it. They’ll keep it to do its bidding, essentially,” Mr Rathbone says. “And those new organisms can be swallowed by other organisms in the same way, sort of like a matryoshka doll.”

In fact, this is likely what happened when about one and a half billion years ago, a cyanobacterium was swallowed by another single-celled organism. The cyanobacteria already had a sophisticated antenna of proteins that trapped every photon of light. But instead of digesting the cyanobacterium, the host organism effectively stripped it for parts – retaining the antenna protein structure that the new organism – the red algae – used for energy.

And when another organism swallowed a red alga to become the first cryptophyte, it was a similar story. Except this time the antenna was brought to the other side of the membrane of the host organism and completely remoulded into new protein shapes that were equally as efficient at trapping sunlight photons.

Evolution

As Prof. Curmi explains, these were the first tiny steps towards the evolution of modern plants and other photosynthetic organisms such as seaweeds.

“In going from cyanobacteria that are photosynthetic, to everything else on the planet that is photosynthetic, some ancient ancestor gobbled up a cyanobacteria which then became the cell’s chloroplast that converts sunlight into chemical energy.

“And the deal between the organisms is sort of like, I’ll keep you safe as long as you do photosynthesis and give me energy.”

One of the collaborators on this project, Dr Beverley Green, Professor Emerita with the University of British Columbia’s Department of Botany says Prof. Curmi was able to make the discovery by approaching the problem from a different angle.

“Paul’s novel approach was to search for ancestral proteins on the basis of shape rather than similarity in amino acid sequence,” she says.

“By searching the 3D structures of two red algal multi-protein complexes for segments of protein that folded in the same way as the cryptophyte protein, he was able to find the missing puzzle piece.”

See the full article here .


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Welcome to University of New South Wales (AU), one of Australia’s leading research and teaching universities. At UNSW, we take pride in the broad range and high quality of our teaching programs. Our teaching gains strength and currency from our research activities, strong industry links and our international nature; UNSW has a strong regional and global engagement.

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Established in 1949, UNSW is a research university, ranked 44th in the world in the 2021 QS World University Rankings and 67th in the world in the 2021 Times Higher Education World University Rankings. UNSW is one of the founding members of the Group of Eight, a coalition of Australian research-intensive universities, and of Universitas 21, a global network of research universities. It has international exchange and research partnerships with over 200 universities around the world.

The university comprises seven faculties, through which it offers bachelor’s, master’s and doctoral degrees. The main campus is in the Sydney suburb of Kensington, 7 kilometres (4.3 mi) from the Sydney CBD. The creative arts faculty, UNSW Art & Design, is located in Paddington, and subcampuses are located in the Sydney CBD as well as several other suburbs, including Randwick and Coogee. Research stations are located throughout the state of New South Wales.

The university’s second largest campus, known as UNSW Canberra(AU) at ADFA, is situated in Canberra, in the Australian Capital Territory (ACT). ADFA is the military academy of the Australian Defence Force, and UNSW Camberra is the only national academic institution with a defence focus.

Foundation

The origins of the university can be traced to the Sydney Mechanics’ School of Arts established in 1833 and the Sydney Technical College established in 1878. These institutions were established to meet the growing demand for capabilities in new technologies as the New South Wales economy shifted from its pastoral base to industries fueled by the industrial age.

The idea of founding the university originated from the crisis demands of World War II, during which the nation’s attention was drawn to the critical role that science and technology played in transforming an agricultural society into a modern and industrial one. The post-war Labor government of New South Wales recognised the increasing need to have a university specialized in training high-quality engineers and technology-related professionals in numbers beyond that of the capacity and characteristics of the existing University of Sydney. This led to the proposal to establish the Institute of Technology, submitted by the then-New South Wales Minister for Education Bob Heffron, accepted on 9 July 1946.

The university, originally named the “New South Wales University of Technology”, gained its statutory status through the enactment of the New South Wales University of Technology Act 1949 (NSW) by the Parliament of New South Wales in Sydney in 1949.

Early years

In March 1948, classes commenced with a first intake of 46 students pursuing programs including civil engineering, mechanical engineering, mining engineering, and electrical engineering. At that time, the thesis programs were innovative. Each course embodied a specified and substantial period of practical training in the relevant industry. It was also unprecedented for tertiary institutions at that time to include compulsory instruction in humanities.

Initially, the university operated from the inner Sydney Technical College city campus in Ultimo as a separate institution from the college. However, in 1951, the Parliament of New South Wales passed the New South Wales University of Technology (Construction) Act 1951 (NSW) to provide funding and allow buildings to be erected at the Kensington site where the university is now located.

The lower campus area of the Kensington campus was vested in the university in two lots, in December 1952 and June 1954. The upper campus area was vested in the university in November 1959.

Expansion

In 1958, the university’s name was changed to the “University of New South Wales” reflecting a transformation from a technology-based institution to a generalist university. In 1960, the faculties of arts and medicine were established, with the faculty of law coming into being in 1971.

The university’s first director was Arthur Denning (1949–1952), who made important contributions to founding the university. In 1953, he was replaced by Philip Baxter, who continued as vice-chancellor when this position’s title was changed in 1955. Baxter’s dynamic, if authoritarian, management was central to the university’s first 20 years. His visionary, but at times controversial, energies saw the university grow from a handful to 15,000 students by 1968. The new vice-chancellor, Rupert Myers (1969–1981), brought consolidation and an urbane management style to a period of expanding student numbers, demand for change in university style, and challenges of student unrest.

In 1962 the academic book publishing company University of New South Wales Press was launched. Now an ACNC not-for-profit entity, it has three divisions: NewSouth Publishing (the publishing arm of the company), NewSouth Books (the sales, marketing and distribution part of the company), and the UNSW Bookshop, situated at the Kensington campus.

The stabilizing techniques of the 1980s managed by the vice-chancellor, Michael Birt (1981–1992), provided a firm base for the energetic corporatism and campus enhancements pursued by the subsequent vice-chancellor, John Niland (1992–2002). The 1990s had the addition of fine arts to the university. The university established colleges in Newcastle (1951) and Wollongong (1961), which eventually became the University of Newcastle and the University of Wollongong in 1965 and 1975, respectively.

The former St George Institute of Education (part of the short-lived Sydney College of Advanced Education) amalgamated with the university from 1 January 1990, resulting in the formation of a School of Teacher Education at the former SGIE campus at Oatley. A School of Sports and Leisure Studies and a School of Arts and Music Education were also subsequently based at St George. The campus was closed in 1999.

Recent history

In 2010 the Lowy Cancer Research Centre, Australia’s first facility to bring together researchers in childhood and adult cancer, costing $127 million, opened.

In 2003, the university was invited by Singapore’s Economic Development Board to consider opening a campus there. Following a 2004 decision to proceed, the first phase of a planned $200 m campus opened in 2007. Students and staff were sent home and the campus closed after one semester following substantial financial losses.

In 2008, it collaborated with two other universities in forming The Centre for Social Impact. In 2019, the university moved to a trimester timetable as part of UNSW’s 2025 Strategy. Under the trimester timetable, the study load changed from offering four subjects per 13-week semester, to three subjects per 10-week term. The change to trimesters has been widely criticised by staff and students as a money-making move, with little consideration as to the well-being of students.

In 2012 UNSW Press celebrated its 50th anniversary and launched the UNSW Bragg Prize for Science Writing. The annual Best Australian Science Writing anthology contains the winning and shortlisted entries among a collection of the year’s best writing from Australian authors, journalists and scientists and is published annually in the NewSouth imprint under a different editorship. The UNSW Press Bragg Student Prize celebrates excellence in science writing by Australian high school students and is supported by the Copyright Agency Cultural Fund and UNSW Science.

In the 2019 Student Experience Survey, the University of New South Wales recorded the lowest student satisfaction rating out of all Australian universities, with an overall satisfaction rating of 62.9, which was lower than the overall national average of 78.4. UNSW’s low student satisfaction numbers for 2019 was attributed to the university’s switch to a trimester system.

On 15 July 2020, the university announced 493 job cuts and a 25 percent reduction in management due to the effects of COVID-19 and a $370 million budget shortfall.

Research centres

The university has a number of purpose-built research facilities, including:

UNSW Lowy Cancer Research Centre is Australia’s first facility bringing together researchers in childhood and adult cancers, as well as one of the country’s largest cancer-research facilities, housing up to 400 researchers.
The Mark Wainwright Analytical Centre is a centre for the faculties of science, medicine, and engineering. It is used to study the structure and composition of biological, chemical, and physical materials.
UNSW Canberra Cyber is a cyber-security research and teaching centre.
The Sino-Australian Research Centre for Coastal Management (SARCCM) has a multidisciplinary focus, and works collaboratively with the Ocean University of China [中國海洋大學; pinyin: Zhōngguó; Hǎiyáng Dàxué](CN) in coastal management research.