Differential transcriptomic and circadian regulation in giant kelp blades based on relative tissue age

Kelp blades grow through cell proliferation at the proximal meristem and erodes from the distal end, resulting in a spatiotemporal map reflecting tissue development. Diel physiology such as photosynthesis, respiration, and carbohydrate metabolism changes across the growing blade yet no one has explicitly tested the interaction of the circadian clock with age/blade structure. Here, we sampled the proximal and distal ends of giant kelp (Macrocystis pyrifera) blades over 48h under constant lab conditions to compare differential transcriptomic and circadian regulation across the blade. This is the first evidence of dynamic circadian regulation in kelp. The interlocked developmental/temporal networks evoked here are integral in understanding the coordination of physiology important to kelp growth and health.