Chlamydomonas proteases: classification, phylogeny, and molecular mechanisms

Abstract

Proteases can regulate myriads of biochemical pathways by digesting or processing target proteins. While up to 3% of eukaryotic genes encode proteases, only a tiny fraction of proteases are mechanistically understood. Furthermore, most of the current knowledge about proteases is derived from studies of a few model organisms, including Arabidopsis thaliana in the case of plants. Proteases in other plant model systems are largely terra incognita limiting our mechanistic comprehension of the post-translational regulation in plants and hampering integrated understanding of how proteolysis evolved. We argue that unicellular green alga Chlamydomonas reinhardtii has a number of technical and biological advantages for systematic studies of proteases, including reduced complexity of many protease families and ease of cell phenotyping. With this end in view, we share a genome-wide inventory of proteolytic enzymes in Chlamydomonas, compare protease degradomes of Chlamydomonas vs Arabidopsis, and dwell on the phylogenetic relatedness of Chlamydomonas proteases to major taxonomic groups. Finally, we summarize the current knowledge of the biochemical regulation and physiological roles of proteases in this algal model. We anticipate that our survey will promote and streamline future research on Chlamydomonas proteases, generating new insights into proteolytic mechanisms and evolution of digestive and limited proteolysis.

Pilot-Scale Cultivation of the Snow Alga Chloromonas typhlos in a Photobioreactor

“…When looking at a 24-h period, without artificial light added on days 3, 4, and 5, a typical pattern can be observed, pointing toward a diurnal rhythm. The cell cycle of photosynthetic microalgae is influenced by a day-night regime in which cell growth (G1) takes place during the light phase (daytime), and the reproductive, cell division phase (S/M) occurs during the dark period (nighttime) ( Cross and Umen, 2015 ; Ivanov et al, 2019 ; Zou and Bozhkov, 2021 ). The NTU profile ( Figure 5A ) can be linked to this diurnal rhythm.…”

“…The steady increase in NTU a few hours after sunrise to sunset follows the cell growth: the enlargement of the cells and increase in dry weight ( Lien and Knutsen, 1979 ; Spudich and Sager, 1980 ; Ostgaard and Jensen, 1982 ; Bišová and Zachleder, 2014 ; de Winter et al, 2017b ). After sunset and during the night, the NTU fluctuated little, which can be linked to the cells no longer growing but dividing within the parental cell ( Harper, 1999 ; Cross and Umen, 2015 ; Ivanov et al, 2019 ; Zou and Bozhkov, 2021 ). Throughout warmer periods, the NTU decreased more overnight, which can be linked to the loss of biomass during the night.…”

“…As daughter cells are released from the parental cell at the end of the dark period ( Mihara and Hase, 1971 ; Vítová and Zachleder, 2005 ; Harris et al, 2009 ; Bišová and Zachleder, 2014 ; Zou and Bozhkov, 2021 ), although it can extend into the light period ( Eschbach et al, 2005 ), many new cells are present and able to influence the turbidity measurements when their photosynthetic apparatus is turned on at sunrise. See also Figure 1 for daughter cells still inside the parental cell after multiple fission.…”

Recent Advances in Understanding the Structural and Functional Evolution of FtsH Proteases

“…Green algae are the evolutionary link between cyanobacteria and plants, hence it is unsurprising that the number of FtsH homologs in algae is more than that of cyanobacteria and fewer than plants. For instance, the model green alga C. reinhardtii encodes six FtsH and three FtsHi homologs ( Malnoë et al, 2014 ; Mishra and Funk, 2021 ; Zou and Bozhkov, 2021 ). FtsHi (recently reviewed by Mishra and Funk, 2021 ) represents a clade of FtsH with inactivated proteolytic capacity.…”

The Papain-like Cysteine Protease HpXBCP3 from Haematococcus pluvialis Involved in the Regulation of Growth, Salt Stress Tolerance and Chlorophyll Synthesis in Microalgae

“…In plants and microalgae, proteases play essential roles in organism growth, reproduction, development, photosynthesis, senescence, and environmental stress responses [1,2]. For example, in Chlamydomonas reinhardtii, proteases are involved in the cell division [3].…”