My professional interest is centred on light reactions of photosynthesis. I did a liventiate at UNAM (Mexico) with my thesis on the statistical properties of the fast induction curve of the chlorophyll a fluorescence under the supervison of Blas Lotina and Reto J. Strasser. Thanks to several sponsors (Australian National University, National Council of Science and Technology of Mexico and the Secretariat of Public Education of Mexico), I did my PhD at on the topic of Photosystem II photodamage and phoroprotection at three Universities: ANU, Wagningen UR and Nagoya University. Further on, I worked as a research associate with Chow group at the Research School of Biology, ANU. During that time, I was awarded a Discovery Translational Fund grant by ANU connect ventures; I designed the Biochemistry and Photosystems laboratories at the new Robertson Bldg; and I worked on the topic of coral bleaching in collaboration with Prof. Vass (Hungary) and Dr. Szabo (UTS, Sydney). Later, I was awarded a Technion postdoctoral fellowship to work at the Research Insitute of Galilee (Israel) with Dr. Noy. At the same time, I have been awarded for 2 years visiting fellowship to ANU to work at the Ball and Chow groups. From 2018, I am currently working as a an integrator postdoc at University of Technology Sydney focusing in instrument development and the evolution of the thylakoid membrane.
Can supervise: YES
At UTS, I am working on:
- The development of new techniques to study photosynthesis.
- Evolution of the thylakoid membrane
- Algal and cynobacterial phenomics
- Development of open source instrumentation
At ANU, I am working on:
- Hyperspectral imaging of biological samples
- Plant hydraulics
- Application of Raman spectroscopy for biological samples.
Light stress (photoinhibition and photodamage) of autotrophs.
Evolution of the thylakoid membrane.
Application and development of spectroscopic tools to study biological systems.
Zavafer, A, Gonzalez-Solis, A, Palacios-Bahena, S, Saucedo-Garcia, M, Tapia de Aquino, C, Vazquez-Santana, S, King-Diaz, B & Gavilanes-Ruiz, M 2020, 'Organized Disassembly of Photosynthesis During Programmed Cell Death Mediated By Long Chain Bases', SCIENTIFIC REPORTS, vol. 10, no. 1.View/Download from: Publisher's site
Iermak, I, Szabó, M & Zavafer, A 2020, 'Analysis of OJIP transients during photoinactivation of photosystem ii indicates the presence of multiple photosensitizers in vivo and in vitro', Photosynthetica, vol. 58, no. Special Issue, pp. 497-506.View/Download from: Publisher's site
© The authors. Generally, excessive excitation absorbed by the pigments is considered the cause of PSII photodamage. Previous studies of action spectra of PSII photodamage concluded that shorter wavelengths induce more damage, supporting the hypothesis of the existence of more than one photosensitizer. However, the relative influence of different photosensitizers is still inconclusive. In this work, we have revisited this question by inducing PSII photodamage in vivo and in vitro at two different wavelengths (460 and 660 nm) where the net absorption cross section was the same using equal irradiance. To correlate PSII photodamage with each wavelength band, we followed its time course using the OJIP transient of the chlorophyll fluorescence to determine the possible contributions of photoinhibition by different photosensitizers. We found evidence that at least two sites of photoinactivation of PSII exist.
Zavafer, A, Iermak, I, Cheah, MH & Chow, WS 2019, 'Two Quenchers Formed During Photodamage of Phostosystem II and The Role of One Quencher in Preemptive Photoprotection.', Scientific reports, vol. 9, no. 1.View/Download from: Publisher's site
The quenching of chlorophyll fluorescence caused by photodamage of Photosystem II (qI) is a well recognized phenomenon, where the nature and physiological role of which are still debatable. Paradoxically, photodamage to the reaction centre of Photosystem II is supposed to be alleviated by excitation quenching mechanisms which manifest as fluorescence quenchers. Here we investigated the time course of PSII photodamage in vivo and in vitro and that of picosecond time-resolved chlorophyll fluorescence (quencher formation). Two long-lived fluorescence quenching processes during photodamage were observed and were formed at different speeds. The slow-developing quenching process exhibited a time course similar to that of the accumulation of photodamaged PSII, while the fast-developing process took place faster than the light-induced PSII damage. We attribute the slow process to the accumulation of photodamaged PSII and the fast process to an independent quenching mechanism that precedes PSII photodamage and that alleviates the inactivation of the PSII reaction centre.
Bates, H, Zavafer, A, Szabo, M & Ralph, PJ 2019, 'A guide to Open-JIP, a low-cost open-source chlorophyll fluorometer', PHOTOSYNTHESIS RESEARCH, vol. 142, no. 3, pp. 361-368.View/Download from: Publisher's site
Zavafer, A, Koinuma, W, Chow, WS, Cheah, MH & Mino, H 2017, 'Mechanism of Photodamage of the Oxygen Evolving Mn Cluster of Photosystem II by Excessive Light Energy.', Scientific reports, vol. 7, no. 1, pp. 7604-7604.View/Download from: Publisher's site
Photodamage to Photosystem II (PSII) has been attributed either to excessive excitation of photosynthetic pigments or by direct of light absorption by Mn4CaO5 cluster. Here we investigated the time course of PSII photodamage and release of Mn in PSII-enriched membranes under high light illumination at 460 nm and 660 nm. We found that the loss of PSII activity, assayed by chlorophyll fluorescence, is faster than release of Mn from the Mn4CaO5 cluster, assayed by EPR. Loss of PSII activity and Mn release was slower during illumination in the presence of exogenous electron acceptors. Recovery of PSII activity was observed, after 30 min of addition of electron donor post illumination. The same behavior was observed under 460 and 660 nm illumination, suggesting stronger correlation between excessive excitation and photodamage compared to direct light absorption by the cluster. A unified model of PSII photodamage that takes into account present and previous literature reports is presented.
Osmond, B, Chow, WS, Wyber, R, Zavafer, A, Keller, B, Pogson, BJ & Robinson, SA 2017, 'Relative functional and optical absorption cross-sections of PSII and other photosynthetic parameters monitored in situ, at a distance with a time resolution of a few seconds, using a prototype light induced fluorescence transient (LIFT) device', Functional Plant Biology, vol. 44, no. 10, pp. 985-1006.View/Download from: Publisher's site
The prototype light-induced fluorescence transient (LIFT) instrument provides continuous, minimally intrusive, high time resolution (∼2s) assessment of photosynthetic performance in terrestrial plants from up to 2m. It induces a chlorophyll fluorescence transient by a series of short flashes in a saturation sequence (180 ∼1s flashlets in <380s) to achieve near-full reduction of the primary acceptor QA, followed by a relaxation sequence (RQA; 90 flashlets at exponentially increasing intervals over ∼30ms) to observe kinetics of QA re-oxidation. When fitted by the fast repetition rate (FRR) model (Kolber et al. 1998) the QA flash of LIFT/FRR gives smaller values for FmQA from dark adapted leaves than FmPAM from pulse amplitude modulated (PAM) assays. The ratio FmQA/FmPAM resembles the ratio of fluorescence yield at the J/P phases of the classical O-J-I-P transient and we conclude that the difference simply is due to the levels of PQ pool reduction induced by the two techniques. In a strong PAM-analogous WL pulse in the dark monitored by the QA flash of LIFT/FRR φPSIIWL ≈ φPSIIPAM. The QA flash also tracks PQ pool reduction as well as the associated responses of ETR QA → PQ and PQ → PSI, the relative functional (σPSII) and optical absorption (aPSII) cross-sections of PSII in situ with a time resolution of ∼2s as they relax after the pulse. It is impractical to deliver strong WL pulses at a distance in the field but a longer PQ flash from LIFT/FRR also achieves full reduction of PQ pool and delivers φPSIIPQ ≈ φPSIIPAM to obtain PAM-equivalent estimates of ETR and NPQ at a distance. In situ values of σPSII and aPSII from the QA flash with smaller antenna barley (chlorina-f2) and Arabidopsis mutants (asLhcb2-12, ch1-3 Lhcb5) are proportionally similar to those previously reported from in vitro assays. These direct measurements are further validated by changes in antenna size in response to growth irradiance. We illustrate how the QA flash facilitates our understanding o...
Szabó, M, Larkum, AWD, Suggett, DJ, Vass, I, Sass, L, Osmond, B, Zavafer, A, Ralph, PJ & Chow, WS 2017, 'Non-intrusive assessment of photosystem II and photosystem I in whole coral tissues', Frontiers in Marine Science, vol. 4, pp. 1-12.View/Download from: Publisher's site
© 2017 Szabó, Larkum, Suggett, Vass, Sass, Osmond, Zavafer, Ralph and Chow. Reef building corals (phylum Cnidaria) harbor endosymbiotic dinoflagellate algae (genus Symbiodinium) that generate photosynthetic products to fuel their host's metabolism. Non-invasive techniques such as chlorophyll (Chl) fluorescence analyses of Photosystem II (PSII) have been widely used to estimate the photosynthetic performance of Symbiodinium in hospite. However, since the spatial origin of PSII chlorophyll fluorescence in coral tissues is uncertain, such signals give limited information on depth-integrated photosynthetic performance of the whole tissue. In contrast, detection of absorbance changes in the near infrared (NIR) region integrates signals from deeper tissue layers due to weak absorption and multiple scattering of NIR light. While extensively utilized in higher plants, NIR bio-optical techniques are seldom applied to corals. We have developed a non-intrusive measurement method to examine photochemistry of intact corals, based on redox kinetics of the primary electron donor in Photosystem I (P700) and chlorophyll fluorescence kinetics (Fast-Repetition Rate fluorometry, FRRf). Since the redox state of P700 depends on the operation of both PSI and PSII, important information can be obtained on the PSII-PSI intersystem electron transfer kinetics. Under moderate, sub-lethal heat stress treatments (33 ◦ C for~20 min), the coral Pavona decussata exhibited down-regulation of PSII electron transfer kinetics, indicated by slower rates of electron transport from Q A to plastoquinone (PQ) pool, and smaller relative size of oxidized PQ with concomitant decrease of a specifically-defined P700 kinetics area, which represents the active pool of PSII. The maximum quantum efficiency of PSII (F v /F m ) and functional absorption cross-section of PSII (σ PSII ) remained unchanged. Based on the coordinated response of P700 parameters and PSII-PSI electron transport properties, we propose that...
Zavafer, A, Cheah, MH, Hillier, W, Chow, WS & Takahashi, S 2015, 'Photodamage to the oxygen evolving complex of photosystem II by visible light', SCIENTIFIC REPORTS, vol. 5.View/Download from: Publisher's site
- Research School of Biology, the Australian National University
- Photosystem Instruments