Abstract
While kelps hold significant potential as sustainable food and feed ingredients, their high iodine content remains a key regulatory and processing challenge for widespread commercial utilization and product inclusion. Selection of low-iodine kelps for cultivation might be possible but could lead to increased susceptibility to stresses as iodine has an antioxidant function in kelps. Bromine may also have such a function, and central to the function of both halogens are the vanadium-dependent haloperoxidases (vHPOs). Here, we exposed both the adult sporophyte stage and the microscopic gametophyte stage of sugar kelp (Saccharina latissima L.) to elevated light intensities and studied the physiological responses (growth and elemental composition in sporophytes) as well as the transcriptomic responses (both stages). Although not conclusive, these findings indicate that neither iodine, bromine, nor vHPOs are central to the high-light response in sugar kelp. Rather, a range of other antioxidant systems were upregulated; some of these in both sporophytes and gametophytes. Moreover, there were clear differences among sporophyte individuals both in their growth response to increased light as well as in the content of iodine, bromine and vanadium, indicating that it should be possible to select for these traits through breeding without compromising high light-stress tolerance.