From algae to plants: understanding pyrenoid-based CO-concentrating mechanisms.

Pyrenoids are the key component of one of the most abundant biological CO concentration mechanisms found in nature. Pyrenoid-based CO-concentrating mechanisms (pCCMs) are estimated to account for one third of global photosynthetic CO capture. Our molecular understanding of how pyrenoids work is based largely on work in the green algae Chlamydomonas reinhardtii.

SAGA1 and MITH1 produce matrix-traversing membranes in the CO-fixing pyrenoid.

Approximately one-third of global CO assimilation is performed by the pyrenoid, a liquid-like organelle found in most algae and some plants. Specialized pyrenoid-traversing membranes are hypothesized to drive CO assimilation in the pyrenoid by delivering concentrated CO, but how these membranes are made to traverse the pyrenoid matrix remains unknown. Here we show that proteins SAGA1 and MITH1 cause membranes to traverse the pyrenoid matrix in the model alga Chlamydomonas reinhardtii.

Controls on regional sulphate distribution in shallow groundwater in the western Canadian Interior Plains.

Sulphate (SO), predominantly derived from sulphur (S)-bearing glacial sediments distributed widely across the Canadian Interior Plains, contributes to high groundwater salinity and can be detrimental to riparian and dry-land ecosystems, agricultural production, and water use. While previous researchers investigated SO distribution and dynamics in shallow groundwater at local scales (<1500 km), we examine SO occurrence in groundwater at larger scales, and to depths of ∼150 m, considering variations in geology, glacial history, climate, and geochemical and hydrogeological settings in the Canadian province of Alberta. Sulphate concentrations in groundwater vary considerably, with 15 % of 139,130 samples above the 500 mg/L Canadian drinking water aesthetic objective.