Activities of principal photosynthetic enzymes in green macroalga Ulva linza: functional implication of C4 pathway in CO2 assimilation

Abstract

The green-tide-forming macroalga Ulva linza was profiled by transcriptome sequencing to ascertain whether the alga carries both C 3 and C 4 photosynthesis genes. The key enzymes involved in C 4 metabolism including pyruvate orthophosphate dikinase (PPDK), phosphoenolpyruvate carboxylase (PEPC), and phosphoenolpyruvate carboxykinase (PCK) were found. When measured under normal and different stress conditions, expression of rbcL was higher under normal conditions and lower under the adverse conditions, whereas that of PPDK was higher under some adverse conditions, namely desiccation, high salinity, and low salinity. Both ribulose-1, 5-biphosphate carboxylase (RuBPCase) and PPDK were found to play a role in carbon fixation, with significantly higher PPDK activity across the stress conditions. These results suggest that elevated PPDK activity alters carbon metabolism in U. linza leading to partial operation of the C 4 carbon metabolism, a pathway that, under stress conditions, probably contributes to the hardy character of U. linza and thus to its wide distribution. C 4 pathway, PPDK, RuBPCase, Ulva linza Citation:Xu J F, Zhang X W, Ye N H, et al. Activities of principal photosynthetic enzymes in green macroalga Ulva linza: functional implication of C 4 pathway in CO 2 assimilation.

The nature of the CO2‐concentrating mechanisms in a marine diatom, Thalassiosira pseudonana

“…Although C 4 metabolism in terrestrial plants is usually associated with Kranz-type anatomy (Sage, 2004), some terrestrial plants, such as Borszczowia aralocaspica, perform C 4 -type photosynthesis within one cell (Voznesenskaya et al, 2001). Similarly, in aquatic environments, Hydrilla verticillata, Ottelia alismoides, Egeria densa, Udotea flabellum and Ulva lynza are believed to perform this type of photosynthesis without Kranz anatomy (Reiskind & Bowes, 1991;Magnin et al, 1997;Lara et al, 2002;Xu et al, 2013;Zhang et al, 2014) and so it is feasible that this pathway may be present in diatoms (Kroth, 2015).…”

Saturating light and not increased carbon dioxide under ocean acidification drives photosynthesis and growth in Ulva rigida (Chlorophyta)

“…d 13 C signatures between -32% and -22% are characteristics of C 3 plants while d 13 C between -16& and -10& are typical for C 4 plants (Zeebe and Wolf-Gladrow 2001;Hoefs 2009 and references therein). The natural variations in the d 13 C signature of U. rigida between -22& and -10& point to the possible occurrence of a C 4 photosynthetic carbon fixation pathway, as observed in U. linza (Xu et al 2013).…”

Salinity-Induced Palmella Formation Mechanism in Halotolerant Algae Dunaliella salina Revealed by Quantitative Proteomics and Phosphoproteomics

“…PPDK catalyzes the formation of PEP that is the initial acceptor of CO 2 in C4 pathway. In U. linza , the elevated PPDK transcription and enzyme activity enhanced C4 carbon metabolism under high salinity stress (Xu et al, 2013). In this study, the phosphorylation site T506 of PPDK is localized in beta turn of PEP-utilizers enzyme mobile domain (IPR008279) region (Figure 7A).…”