植物科学

Cyanobacteria are Gram-negative oxygen-producing photosynthetic bacteria that are useful in the pharmaceutical and biofuel industries. Monitoring of oxidative stress under fluctuating environmental conditions is important for determining the fitness, survival, and growth of cyanobacteria in the laboratory as well as in large scale cultivation systems. Here, we provide a protocol developed using unicellular Synechococcus elongatus PCC 7942 and filamentous Fremyella diplosiphon BK14 cyanobacteria for high-throughput oxidative stress measurement by 2′,7′-dichlorodihydrofluorescein-diacetate (DCFH-DA) and flow cytometry (FCM). We also provide details for the optimization of cell number, dye concentration, and FCM parameters for each organism before it can be utilized to quantify reactive oxygen species (ROS). FCM-based method can be used to measure ROS in a large population of cyanobacterial cells in a high-throughput manner.

Graphical abstract:

The brown alga Ectocarpus has a haploid-diploid life cycle that involves alternation between two multicellular generations, the sporophyte and the gametophyte. Life cycle generation is not determined by ploidy but by a genetic system that includes two different three amino acid loop extension homeodomain transcription factors called OUROBOROS and SAMSARA. In addition, sporophytes have been shown to secrete a diffusible factor into the medium that can induce gametophyte initial cells to switch from the gametophyte to the sporophyte developmental program. The protocol presented here describes how to produce sporophyte-conditioned medium containing the diffusible sporophyte-inducing factor and how to assay for activity of the factor using a meio-spore-based bioassay. The protocol, which describes how several steps of these procedures can be optimised, will represent a useful tool for future work aimed at characterising the diffusible factor and investigating its mode of action.

Glutathione is an important molecule involved in the primary and secondary metabolism of all organisms. The Glutathione redox status is an indicator of the cellular redox state. Therefore, it is important to have precise methods on hand to determine the glutathione redox status in the cell. In this protocol, we describe an improved spectrophotometric method to estimate the content of reduced (GSH) and oxidized (GSSG) forms of glutathione in the extremophilic microalga Galdieria phlegrea.

Cryopreservation is commonly used for storing viable cells, tissues, organs or organisms at ultralow temperatures, and usually involves immersion in liquid nitrogen at -196 °C. Here we provide a detailed cryopreservation protocol for C. reinhardtii based on Crutchfield’s work (Crutchfield et al., 1999), with minor changes (Yang and Li, 2016). In this study, we compared the cryoprotection effect of two common cryopreservation agents (CPAs), methanol and DMSO. Furthermore, the two-step cryopreservation process was divided into five stages to study the factors affecting the survival rate at each stage. We found that the use of methanol as the CPA, combined with the cooling process outlined here (cooling from 25 °C to -55 °C at a rate of 1 °C/min), were indispensable for cell survival after cryopreservation. The thawing process described here (thawing at 35 °C for 5 min) was also important for increasing the survival rate.