Figure 8.

Proposed model of disorder adjustment in the development of orthodox seeds. At the beginning of the development of the seed, the biosynthesis of the reserve compounds and the molecules required to grow and develop is active, the available water is abundant, and the content of structured proteins is high (A). As the development program progresses, there is a significant reduction in water content, cell volume is reduced, and macromolecular crowding increases. This effect causes unwanted interactions between proteins, loss of tertiary structure, and protein aggregation. To reduce this negative effect, cells activate protective mechanisms (such as the biosynthesis of compatible solutes and the induction of chaperones). However, we propose that there is also a sharp reduction of the most labile proteins, without the replacement of other types of structured proteins. In contrast, the content of the IDPs increases and all the genes expressed de novo encodes for IDPs (B). The number of structural proteins continues to decrease, as does their content. It is considered that all this complements the typical mechanisms of tolerance to desiccation. In general, this can be considered to be a strategy to make the proteome more resilient to water-limiting conditions by a mechanism mediated by overall adjustment of the protein disorder.