Haim Treves

Tel Aviv University | TAU

Excess illumination damages the photosynthetic apparatus with severe implications with regard to plant productivity. Unlike model organisms, the growth of Chlorella ohadii , isolated from desert soil crust, remains unchanged and photosynthetic O 2 evolution increases, even when exposed to irradiation twice that of maximal sunlight. Spectroscopic, b...

The factors rate-limiting growth of photosynthetic organisms under optimal conditions are controversial [1-8]. Adaptation to extreme environments is usually accompanied by reduced performance under optimal conditions [9, 10]. However, the green alga Chlorella ohadii, isolated from a harsh desert biological soil crust [11-17], does not obey this rul...

The unparalleled performance of Chlorella ohadii under irradiances of twice full sunlight underlines the gaps in our understanding of how the photosynthetic machinery operates, and what sets its upper functional limit. Rather than succumbing to photodamage under extreme irradiance, unique features of photosystem II function allow C. ohadii to maint...

Photosynthesis-related pathways are regarded as a promising avenue for crop improvement. Whilst empirical studies have shown that photosynthetic efficiency is higher in microalgae than in C 3 or C 4 crops, the underlying reasons remain unclear. Using a tailor-made microfluidics labelling system to supply ¹³ CO 2 at steady state, we investigated in...

Chlorella ohadii was isolated from desert biological soil crusts, one of the harshest habitats on Earth, and is emerging as an exciting new green model for studying growth, photosynthesis and metabolism under a wide range of conditions. Here, we compared the genome of C. ohadii, the fastest growing alga on record, to that of other green algae, to r...

Introduction Flux phenotypes from different organisms and growth conditions allow better understanding of differential metabolic networks functions. Fluxes of metabolic reactions represent the integrated outcome of transcription, translation, and post-translational modifications, and directly affect growth and fitness. However, fluxes of intracellu...

The flux in photosynthesis can be studied by performing ¹³CO2 pulse labelling and analysing the temporal labelling kinetics of metabolic intermediates using gas or liquid chromatography linked to mass spectrometry. Metabolic flux analysis (MFA) is the primary approach for analysing metabolic network function and quantifying intracellular metabolic...

Maintaining proper metabolite levels in a complex metabolic network is crucial for maintaining a high flux through the network. In this paper, we discuss major regulatory mechanisms over the Calvin Benson Cycle (CBC) with regard to their roles in conferring homeostasis of metabolite levels in CBC. These include: 1) Redox regulation of enzymes in th...

Cyanobacteria and eukaryotic algae make a major contribution to global photosynthetic productivity. To cope with the low availability of CO 2 in aqueous systems they deploy inorganic carbon-concentrating mechanisms (CCMs). These concentrate CO 2 in microcompartments that contain Rubisco (carboxysomes in cyanobacteria; pyrenoids in green algae). The...

Introduction During the arms race between plants and pathogens, pathogenesis-related proteins (PR) in host plants play a crucial role in disease resistance, especially PR1. PR1 constitute a secretory peptide family, and their role in plant defense has been widely demonstrated in both hosts and in vitro. However, the mechanisms by which they control...

Botany-derived antimicrobial peptides (BAMPs), a class of small, cysteine-rich peptides produced in plants, are an important component of the plant immune system. Both in vivo and in vitro experiments have demonstrated their powerful antimicrobial activity. Besides in plants, BAMPs have cross-kingdom applications in human health, with toxic and/or...

Photosynthesis in deserts is challenging since it requires fast adaptation to rapid night-to-day changes, that is, from dawn’s low light (LL) to extreme high light (HL) intensities during the daytime. To understand these adaptation mechanisms, we purified photosystem I (PSI) from Chlorella ohadii, a green alga that was isolated from a desert soil c...

The green alga Chlorella sp. and the filamentous cyanobacterium Leptolyngbya sp., regularly cope with various stressors including frequent hydration–desiccation cycles. When grown in axenic cultures, Chlorella sp. is unable to resurrect even after very slow desiccation unless desiccation takes place in the presence of Leptolyngbya sp. or a lysate t...

The surface of sandy deserts is one of the most inhospitable environments on the planet, yet some organisms have evolved remarkable adaptations that allow them to survive such harsh conditions. This is the story of one of them - a humble single-celled alga. By Haim Treves and Mark Stitt Desert biological sand crusts are one of the harshest environ...

Filamentous cyanobacteria are the main founders and primary producers in biological desert soil crusts (BSCs) and are likely equipped to cope with one of the harshest environmental conditions on earth including daily hydration/dehydration cycles, high irradiance and extreme temperatures. Here we resolved and report on the genome sequence of Leptoly...

Organisms inhabiting biological soil crusts (BSCs) are able to cope with extreme environmental conditions including daily hydration/dehydration cycles, high irradiance and extreme temperatures. The photosynthetic machinery, potentially the main source of damaging reactive oxygen species during cessation of CO2 fixation in desiccating cells, must be...

Environmental research often faces two major hurdles: (i) fluctuating spatial and temporal conditions and consequently large variability in the organisms' abundance and performance, (ii) complex, costly logistics involved in field experiments. Measurements of physiological parameters or molecular analyses often represent single shot experiments. To...

Desert biological soil crusts (BSCs) are formed by adhesion of soil particles to polysaccharides excreted by filamentous cyanobacteria, the pioneers and main producers in this habitat. Biological soil crust destruction is a central factor leading to land degradation and desertification. We study the effect of BSC structure on cyanobacterial activit...

We recently isolated a small green alga from a biological sand crust (BSC) in the NW Negev, Israel. Based on its 18S rDNA and rbcL genes it is a close relative of Chlorella sorokiniana and of certain strains of C. vulgaris and C. variabilis, but differs substantially in many aspects from C. sorokiniana. Since the classification of Chlorellales is s...

It is no secret that our climate is changing – rapidly – and together with it, oceans change as well. The Intergovernmental Panel on Climate Change (IPCC), consisting of hundreds of scientists worldwide, have shown that changes in global climate have accelerated since the 1750s, causing an overall increase in temperature both on land and in the sea...