Chlamydomonas reinhardtii: duration of its cell cycle and phases at growth rates affected by temperature

Abstract

Synchronized cultures of the green alga Chlamydomonas reinhardtii were grown photoautotrophically under a wide range of environmental conditions including temperature (15-37 °C), different mean light intensities (132, 150, 264 μmol m⁻² s⁻¹), different illumination regimes (continuous illumination or alternation of light/dark periods of different durations), and culture methods (batch or continuous culture regimes). These variable experimental approaches were chosen in order to assess the role of temperature in the timing of cell division, the length of the cell cycle and its pre- and post-commitment phases. Analysis of the effect of temperature, from 15 to 37 °C, on synchronized cultures showed that the length of the cell cycle varied markedly from times as short as 14 h to as long as 36 h. We have shown that the length of the cell cycle was proportional to growth rate under any given combination of growth conditions. These findings were supported by the determination of the temperature coefficient (Q₁₀), whose values were above the level expected for temperature-compensated processes. The data presented here show that cell cycle duration in C. reinhardtii is a function of growth rate and is not controlled by a temperature independent endogenous timer or oscillator, including a circadian one.

LHCSR Expression under HSP70/RBCS2 Promoter as a Strategy to Increase Productivity in Microalgae

“…Consistently, the specific growth rate (μ) calculated for transformed lines was increased by ~18% compared to WT (Figure 8E). It is worth to note that the specific growth rates reported in Figure 8D are consistent with previous growth rates reported for C. reinhardtii [45,46,47,48]. Photosynthetic efficiency of WT and transformed cultures were then calculated considering the total amount of photons received by the cultures and the energy stored as dry weight biomass at the end of growth curves; WT cells exhibited a photosynthetic efficiency of 3.4%, while transformed lines scored photosynthetic efficiencies of 4.4–4.7% (Figure 8F).…”

“…At the end of the exponential phase of growth, the cells were counted at the microscope using an improved Neubauer hematocytometer. Specific growth rates were calculated from liner regression of the exponential growth phase in logarithmic scale as described in [48]. Cell dry weight was measure upon drying biomass for 4 days at 60 °C.…”

Mechanosensitive physiology of chlamydomonas reinhardtii under direct membrane distortion

“…4 were taken over 24 h. Cell division occurred within 12 h in the both cases (uncompressed and compressed), but the FACS data was different each other at 12 h. For uncompressed cell, the fraction of cell cycle was divided into two main peaks. The distribution of cell number was gradually crowded in G 1 phase at 24 h and 48 h compared with the initial time because C. reinhardtii in normal state had 16 h for total cell cycle time as known by Vitova M. et al21 (Fig. 3c and Supplementary Fig.…”

The Chlamydomonas cell cycle

“…Although there is general agreement on the existence and overall long duration of the post‐commitment G1 period, relative to the total time in G1, there is no consensus on how its length is controlled. John and co‐workers described this period as timer controlled, an observation that is generally supported by experiments where division occurs at approximately the same time across a range of post‐commitment growth rates (McAteer et al ., ); however, other researchers have reported variability in the post‐commitment interval (Oldenhof et al ., ; Vítová et al ., ,b). Despite some experimental variability, the overall timing of cell‐cycle events in Chlamydomonas when grown under a variety of diurnal regimes (e.g.…”