Oral: Understanding the orgins for the multiple condesates in the photsynthetic algae Chlamydomonas reinhardtii saga1 mutant

Eukaryotic algae contribute to about a third of carbon fixation around the world. This powerful mechanism is attributed to a small liquid-like organelle called the pyrenoid. In alga like Chlamydomonas Reinhardtii, the pyrenoid is made up of three major components; a phase separated matrix of carbon-fixing enzymes called Rubisco, a tubule network that delivers CO2 to this matrix, and a starch sheath that binds (and surrounds) the outside of this matrix. Previous studies have shown if the SAGA1 protein is removed, the resulting mutant has multiple small condensates. The origin of these multiple small condensates is not well understood. To understand the mechanism further, we remove KEY1, a kinase that controls dissolution during cell division in the wild-type and also results in multiple large condensates, in the saga1 to test if the small condensates formed in the saga1 mutant are capable of condensing into larger condensates. Our results show that in the absence of SAGA1 and KEY1 these condensates are unable to condense to the same number of condensates as the key1 mutant. This indicates that both SAGA1 and KEY1 are needed to coarsen to a larger condensate and implies a potential role that the tubule network itself plays in the formation of a single pyrenoid.