Involvement of ethylene and nitric oxide in cell death in mastoparan‐treated unicellular alga Chlamydomonas reinhardtii

Abstract

This work demonstrates a contribution of ethylene and NO (nitric oxide) in MP (mastoparan)-induced cell death in the green algae Chlamydomonas reinhardtii. Following MP treatment, C. reinhardtii showed massive cell death, expressing morphological features of PCD (programmed cell death). A pharmacological approach involving combined treatments with MP and ethylene- and NO-interacting compounds indicated the requirement of trace amounts of both ethylene and NO in MP-induced cell death. By employing a carbon dioxide laser-based photoacoustic detector to measure ethylene and a QCL (quantum cascade laser)-based spectrometer for NO detection, simultaneous increases in the production of both ethylene and NO were observed following MP application. Our results show a tight regulation of the levels of both signalling molecules in which ethylene stimulates NO production and NO stimulates ethylene production. This suggests that, in conjunction with the elicitor, NO and ethylene cooperate and act synchronously in the mediation of MP-induced PCD in C. reinhardtii. To the best of our knowledge, this is the first report on the functional significance of ethylene and NO in MP-induced cell death.

Nitric Oxide–Triggered Remodeling of Chloroplast Bioenergetics and Thylakoid Proteins upon Nitrogen Starvation inChlamydomonas reinhardtii

“…NaR activity appears also dispensable for nitrite-dependent NO synthesis in Scenedesmus (Mallick et al, 1999) but seems required for NO evolution from nitrite by C. reinhardtii cells grown in nitrogenreplete conditions (Sakihama et al, 2002). However, NO production by NaR-defective mutants has been documented during hypoxia (Hemschemeier et al, 2013a) in mastoparan-treated cells (Yordanova et al, 2010) or in iron-limited cultures exposed to CO (Liping et al, 2013). Together, these results point to the prevalence of alternative NO-producing pathways in C. reinhardtii, probably coupled to the increased catabolism of amino acids and nucleotides undergone by nitrogen-starved cells.…”

“…At this stage, we cannot yet assess properly the respective contributions to the loss of the cytochrome b 6 f complex of (1) protein posttranslational modifications (nitrosylation) that would target them for degradation and (2) activation of a NO signal transduction pathway. NO has been involved in a number of signaling pathways in C. reinhardtii, including acclimation to anaerobiosis (Hemschemeier et al, 2013a), iron homeostasis (Liping et al, 2013), cell death (Yordanova et al, 2010), copper stress (Zhang et al, 2008), and regulation of nitrogen assimilation As indicated in the balloon, NO contributes to the loss of the cytochrome b 6 f complex by tagging cytochrome b 6 f subunits and related proteins for degradation and/or by participating in a signal transduction pathway leading to gene activation and degradation of the cytochrome b 6 f complex. Enzymes or genetic contexts that favor the accumulation of nitrite and the production of NO are shown in black, while those counteracting these processes are shown in gray.…”

Two Calcium-Dependent Protein Kinases fromChlamydomonas reinhardtiiare transcriptionally regulated by nutrient starvation

“…[21][22][23][24][25][26][27] As mentioned earlier, since Ca 2+ is known to be involved in several stress induced phenomenons of Chlamydomonas, we set out to explore the regulation of the 2 CDPKs, CDPK1 and CDPK3, under varying stress conditions by studying their transcript profiles using RT-PCR.…”

An organelle K+ channel is required for osmoregulation in Chlamydomonas reinhardtii

“…The cell viability assay was performed following a previously published protocol (Yordanova et al, 2010). In brief, a stock fluorescein diacetate (FDA) (Sigma) solution was prepared in advance by dissolving 5 mg/ml in DMSO and stored at −20°C.…”