The formation, function and fate of protein storage compartments in seeds

Abstract

Seed storage proteins (SSPs) have been studied for more than 250 years because of their nutritional value and their impact on the use of grain in food processing. More recently, the use of seeds for the production of recombinant proteins has rekindled interest in the behavior of SSPs and the question how they are able to accumulate as stable storage reserves. Seed cells produce vast amounts of SSPs with different subcellular destinations creating an enormous logistic challenge for the endomembrane system. Seed cells contain several different storage organelles including the complex and dynamic protein storage vacuoles (PSVs) and other protein bodies (PBs) derived from the endoplasmic reticulum (ER). Storage proteins destined for the PSV may pass through or bypass the Golgi, using different vesicles that follow different routes through the cell. In addition, trafficking may depend on the plant species, tissue and developmental stage, showing that the endomembrane system is capable of massive reorganization. Some SSPs contain sorting signals or interact with membranes or with other proteins en route in order to reach their destination. The ability of SSPs to form aggregates is particularly important in the formation or ER-derived PBs, a mechanism that occurs naturally in response to overloading with proteins that cannot be transported and that can be used to induce artificial storage bodies in vegetative tissues. In this review, we summarize recent findings that provide insight into the formation, function, and fate of storage organelles and describe tools that can be used to study them.

Integral Proteins in Plant Oil Bodies

“…Plant cells deposit storage resources of carbohydrates, proteins, and neutral lipids in subcellular particles termed starch granules, protein bodies, and oil bodies, respectively. In contrast with the active studies of protein bodies and starch granules [1][2][3][4][5][6], research progress on oil bodies is relatively late and slow presumably due to less research input and inevitable technical problems caused by the hydrophobic features of these lipid-storage organelles.…”

Increasing the production yield of recombinant protein in transgenic seeds by expanding the deposition space within the intracellular compartment

“…7 On the other hand, in dicotyledonous plants such as soybean, pea and sunflower, 7S and 11S globulins are specifically and predominantly expressed in the embryos of maturing seeds. 8 Notably, the endosperm tissue of cereal seeds occupies more than 80% of the total seed weight and represents a stable storage organ. Many seedspecific promoters have been isolated from several crops and used for the expression of recombinant proteins in transgenic plants.…”

Storage compounds, ABA and fumarase in Fagus sylvatica embryos during stratification

“…In the cotyledons of beech seeds, the majority of storage proteins correspond to 11S legumin-type and 7S vicilin-type globulins (Collada et al 1993). They are accumulated in PSVs rather than in protein bodies (Ibl and Stoger 2012). The first changes of PSVs were observed during the first week of stratification and they probably correlate with the increase of water content in embryos after imbibition.…”

“…Seed cells usually contain several different storage organelles including dynamic protein vacuoles in which storage proteins are deposited during seed development. Storage proteins can be transported from vacuoles through the cell (Ibl and Stoger 2012). Partial mobilization of storage proteins starts with the uptake of water by dry seeds (Bewley et al 2013).…”