Molecular dynamics of seed priming at the crossroads between basic and applied research

Abstract

Key message The potential of seed priming is still not fully exploited. Our limited knowledge of the molecular dynamics of seed pre-germinative metabolism is the main hindrance to more effective new-generation techniques. Abstract Climate change and other recent global crises are disrupting food security. To cope with the current demand for increased food, feed, and biofuel production, while preserving sustainability, continuous technological innovation should be provided to the agri-food sector. Seed priming, a pre-sowing technique used to increase seed vigor, has become a valuable tool due to its potential to enhance germination and stress resilience under changing environments. Successful priming protocols result from the ability to properly act on the seed pre-germinative metabolism and stimulate events that are crucial for seed quality. However, the technique still requires constant optimization, and researchers are committed to addressing some key open questions to overcome such drawbacks. In this review, an update of the current scientific and technical knowledge related to seed priming is provided. The rehydration–dehydration cycle associated with priming treatments can be described in terms of metabolic pathways that are triggered, modulated, or turned off, depending on the seed physiological stage. Understanding the ways seed priming affects, either positively or negatively, such metabolic pathways and impacts gene expression and protein/metabolite accumulation/depletion represents an essential step toward the identification of novel seed quality hallmarks. The need to expand the basic knowledge on the molecular mechanisms ruling the seed response to priming is underlined along with the strong potential of applied research on primed seeds as a source of seed quality hallmarks. This route will hasten the implementation of seed priming techniques needed to support sustainable agriculture systems.

Seed longevity and genome damage

“…Primed seeds are then re-dried before completion of germination and loss of desiccation tolerance. Seedling establishment for many commercial species, typically >70% in the case of sugar beet, can be increased ∼10% by vigour enhancement through seed priming [ 129 ]. The improved growth vigour of primed seeds also confers resistance to biotic and abiotic stresses encountered in the field, resulting in significant and sustainable yield increases [ 29 ].…”

“…Seed imbibition is reversible (VIII): seeds in the soil undergo hydration-desiccation cycles. Commercial seed priming technologies hydrate seeds, followed by a dry back, to facilitate cellular repair and improve the vigour of germination and seedling growth [ 128 , 129 ]. Desiccation tolerance is lost as seeds progress to germination but can be re-established by treatment with ABA or PEG (IX) allowing survival after re-drying [ 13 ].…”

Noninvasive Methods to Detect Reactive Oxygen Species as a Proxy of Seed Quality

“…Fast and uniform seed germination and successful seedling establishment are high priorities for enhancing crop yields. Technologies designed to improve germination performance (generally known as seed priming) can contribute to building up dynamic and sustainable agriculture practices [ 25 , 26 , 27 ]. Seed priming is the process of regulating seed germination by managing a series of parameters during the initial stages of germination [ 28 , 29 , 30 ].…”

“…For instance, the so-called “on-farm” seed priming, a low-cost technique consisting of soaking seeds in water before sowing, has led to 22% faster seed emergence translated into a 21% yield increase, whereas under stress conditions the plants proved to be more tolerant, gaining up to 22–28% in yield improvements [ 31 ]. The main effect of priming is the activation of the metabolic processes triggered during the early phase of germination, or the pre-germinative metabolism [ 16 , 27 , 28 ]. Although the success of seed priming is strongly correlated to plant species, genotype, seed lot, and vigor, it has also been proven to be effective in improving germination performances during environmental constraints [ 28 , 29 , 32 , 33 , 34 ].…”

“…Despite its simplicity, hydropriming has been reported to improve germination performances (in terms of germination time, speed, and percentage) in many species [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. In the case of some practices (e.g., osmopriming, chemopriming), several studies have indicated that these act by delaying water entrance into the seed and thus may limit ROS oxidative injury [ 42 , 43 , 44 ], whereas in most cases priming acts at the level of seed transition from dormancy toward full germination, touching processes like the activation of DNA repair and antioxidant mechanisms, essential to obtain seeds with improved quality (see comprehensive reviews [ 16 , 27 , 28 ]). When considering the antioxidant response, enhanced enzymatic activity or increased expression of genes encoding antioxidant enzymes (e.g., SOD, APX, CAT, GR), were evidenced during seed germination and priming treatments [ 45 , 46 , 47 , 48 ].…”