Seed Aging and Repair: The Natural Protection and Repair Mechanism.

The natural protection and repair mechanism (NPRM) has long been recognized, in orthodox seeds, as the means by which the cells comprising the propagule prepare for, and survive, extreme water loss. Although anhydrobiosis (life with little water) is not restricted to seeds, our fascination with it in seeds stems from the fact that this capacity underpins agriculture, permitting seeds from this harvest to be held over to sow next season's crop, perpetuating the human food supply in both the short- and long-terms. The resilience of seeds in the dehydrated state also makes them a superlative means for global food distribution. So, what is this, “natural protection and repair mechanism”, upon which we are so utterly dependent, and how does it work? The NPRM is an umbrella term referring to any physical or physiological alteration that renders the cell: 1) more tolerant of water loss and attendant stresses and; 2) better able to repair the damage to macromolecules and cellular components, accrued during the sojourn in the dehydrated state, upon subsequent rehydration (imbibition). The more competent the cells comprising the seed are at performing these tasks, the greater their longevity and the more superior their vigor. Such a broad, axiomatic definition of the NPRM has resulted in a partitioning of the process, identifying cellular constituents perceived as requiring protection/repair (membranes, DNA, the proteome) and entities thought to impart it. We have focused on the proteome and are attempting to identify those proteins most susceptible to damage and/or most dependent on repair, the so-called “weakest links” in seed longevity. A plethora of molecular techniques and genetic approaches have identified those proteins involved in translation as an Achilles heel in seed longevity. Additional evidence has implicated an enhanced potential for glycation in the embryo as conducive to seed “aging” in the dehydrated state.