I'll have a go. Disclaimer: I'm not a biologist; corrections welcome.
Consider a growing multicellular organism. It grows by a process of cell division. Each division turns one cell into two adjacent cells. The structure it ends up with will depend on the orientation of those dividing cells (you'll tend to get growth "along the axis of division", so to speak).
A wide variety of multicellular organisms have a mechanism that orients cells according to features on the outside of neighbouring cells. (It "mediates spindle orientation in diverse animal taxa by linking microtubule motor proteins to a marker protein on the cell cortex localized by external cues", as the abstract puts it. The "mitotic spindle" is a structure involved in cell division, also called mitosis. It's mostly made out of long thin things called microtubules, and its job is to separate the chromosomes for the two new cells, which it does using "motor proteins". The cell cortex is the inner surface of the boundary of the cell.)
One part of this process is the way in which a protein involved in the mitotic spindle attaches itself to that thing on the cell cortex. The relevant bit of that protein is called the "guanylate kinase protein interaction domain" or GK_PID for short. A protein interaction domain is a bit of protein that interacts with other things; multiple different proteins can contain instances of the same interaction domain, just as multiple different programs can contain (say) the same code for computing SHA-256 checksums.
The paper reports evidence that a single mutation enabled the GK_PID to attach itself to the marker on the cell cortex. ("The complex was assembled through a series of molecular exploitation events, one of which – the evolution of GK_PID’s capacity to bind the cortical marker protein – can be recapitulated by reintroducing a single historical substitution into the reconstructed ancestral GK_PID."
So. This doesn't say that multicellularity was enabled by a single mutation. It says that one small but important part of a process that's necessary for complex multicellular organisms was enabled by a single mutation. Still pretty cool, but the journalistic science->hype conversion machine is clearly operating as usual here.
Consider a growing multicellular organism. It grows by a process of cell division. Each division turns one cell into two adjacent cells. The structure it ends up with will depend on the orientation of those dividing cells (you'll tend to get growth "along the axis of division", so to speak).
A wide variety of multicellular organisms have a mechanism that orients cells according to features on the outside of neighbouring cells. (It "mediates spindle orientation in diverse animal taxa by linking microtubule motor proteins to a marker protein on the cell cortex localized by external cues", as the abstract puts it. The "mitotic spindle" is a structure involved in cell division, also called mitosis. It's mostly made out of long thin things called microtubules, and its job is to separate the chromosomes for the two new cells, which it does using "motor proteins". The cell cortex is the inner surface of the boundary of the cell.)
One part of this process is the way in which a protein involved in the mitotic spindle attaches itself to that thing on the cell cortex. The relevant bit of that protein is called the "guanylate kinase protein interaction domain" or GK_PID for short. A protein interaction domain is a bit of protein that interacts with other things; multiple different proteins can contain instances of the same interaction domain, just as multiple different programs can contain (say) the same code for computing SHA-256 checksums.
The paper reports evidence that a single mutation enabled the GK_PID to attach itself to the marker on the cell cortex. ("The complex was assembled through a series of molecular exploitation events, one of which – the evolution of GK_PID’s capacity to bind the cortical marker protein – can be recapitulated by reintroducing a single historical substitution into the reconstructed ancestral GK_PID."
So. This doesn't say that multicellularity was enabled by a single mutation. It says that one small but important part of a process that's necessary for complex multicellular organisms was enabled by a single mutation. Still pretty cool, but the journalistic science->hype conversion machine is clearly operating as usual here.