Handing off iron to the next generation: how does it get into seeds and what for?

Abstract

To ensure the success of the new generation in annual species, the mother plant transfers a large proportion of the nutrients it has accumulated during its vegetative life to the next generation through its seeds. Iron (Fe) is required in large amounts to provide the energy and redox power to sustain seedling growth. However, free Fe is highly toxic as it leads to the generation of reactive oxygen species. Fe must, therefore, be tightly bound to chelating molecules to allow seed survival for long periods of time without oxidative damage. Nevertheless, when conditions are favorable, the seed's Fe stores have to be readily remobilized to achieve the transition toward active photosynthesis before the seedling becomes able to take up Fe from the environment. This is likely critical for the vigor of the young plant. Seeds constitute an important dietary source of Fe, which is essential for human health. Understanding the mechanisms of Fe storage in seeds is a key to improve their Fe content and availability in order to fight Fe deficiency. Seed longevity, germination efficiency and seedling vigor are also important traits that may be affected by the chemical form under which Fe is stored. In this review, we summarize the current knowledge on seed Fe loading during development, long-term storage and remobilization upon germination. We highlight how this knowledge may help seed Fe biofortification and discuss how Fe storage may affect the seed quality and germination efficiency.

Subcellular dynamics studies of iron reveal how tissue‐specific distribution patterns are established in developing wheat grains

“…S11. It is currently unclear how iron is transported through the plant cytosol, although NA is thought to play a key role (Mari et al ., 2020). Our study suggests that vesicle transport could also be involved.…”

“…The molecular pathways of iron and zinc uptake from the soil into plant roots are relatively well understood, but we know little about mineral loading into the seeds and subsequent distribution to different tissues (Mari et al ., 2020). Recent isotope labelling studies in Arabidopsis suggested that virtually all the iron in seeds was remobilized from senescing leaves (and other organs) with only an indirect contribution from uptake by the roots (Pottier et al ., 2019).…”

“…Physical separation between the tissues of the mother plant and the seed (the filial generation) means that iron is secreted and then taken up again by the developing zygote (Mari et al ., 2020). Nutrients are delivered to the developing grain via the vascular bundle which runs through the ventral crease in wheat, and the nucellar projection.…”

Subcellular dynamics studies reveal how tissue-specific distribution patterns of iron are established in developing wheat grains

“…Fig S11. It is currently unclear how iron is transported through the plant cytosol, although NA is thought to play a key role (Mari et al, 2020). Our study suggests that vesicle transport could also be involved.…”

“…5). NA is known to be important for iron loading into the grain (Mari et al, 2020). Interestingly, two different NAS genes were upregulated in aleurone and starchy endosperm, TaNAS9 and TaNAS6 , respectively.…”