Late Embryogenesis Abundant (LEA) proteins are hypothesized to play a major role in preserving the cellular milieu from damage upon water loss in bacteria, fungi, lichens, resurrection plants, some animals and orthodox plant seeds. The focus of the current endeavor is to identify how the members of the nine different families of LEA proteins exert protective influence over members of a stress-susceptible proteome. Representative LEA proteins have been demonstrated to protect cells from dehydration stress but other LEA proteins can protect cells from salt, heat-, or cold-stress. Protection against stresses has been demonstrated transgenically across kingdoms. Hence, the accepted paradigm in cell biology is that LEA proteins are general molecular shields exerting a protective effect for proteins and/or membranes independent of co-evolved molecular contexts. We challenge this tenet observing that distinct phenotypes from mutant plants dysfunctional for a single LEA exist suggesting that some LEA proteins act neither broadly nor redundantly. A new LEA paradigm accepts that there are some preferred (1°) LEA protein-client molecule interactions. This hypothesis does not refute the perception that LEA proteins have a variety of client molecules with which they interact, but it does refine it to suggest that there may be a ranking of such client molecules for any LEA protein such that some are preferred above others. This obviates LEA redundancy and explains the observed phenotypes upon specific LEA dysfunction. Those studying LEA proteins’ membrane protective properties were first to demonstrate that such LEA proteins interact preferentially with membranes of specific lipid compositions, usually mixtures that most closely resemble the organelle in which the LEA protein is resident. There are examples of other intrinsically disordered proteins that are capable of specifically interacting with a small number of preferred client proteins (1° CPs). The implications for using such LEA protein-client protein interactions (when known) to understand LEA functional interactomes are profound. Hence, we have initiated exploration of specific LEA protein 1° CP interactions. 

  A long-term research collaboration, headed by the lab of Prof. Tianyong Zhao, Northwest Agriculture and Forestry University, Yangling, Shaanxi, China, which includes my lab, seeks to understand how soluble sugars influence seed longevity.  

  Since the discovery of raffinose in plant extracts (Loiseau, 1876) scientists have pondered the role they may play. The raffinose family oligosaccharides (RFOs) have long posed a quandary to seed biologists and physiologists interested in abiotic stress tolerance. Although there are many reports of a positive correlation of the RFOs with survival of dehydration of plant cells (programmed [seeds] or imposed [drought stress]) no definitive example of the RFOs being required for, or even aiding in, survival of dehydration have yet been provided. Suggested roles for RFOs have ranged from acting as stress signaling molecules, assisting sucrose form the glassy state as seed cells undergo maturation desiccation, and as free radicle scavenging molecules. Reduction of raffinose amounts however, are apparently without consequence in soybean and Arabidopsis while correlations with glassy state formation have been called into question. Nevertheless, overexpression of GALACTINOL SYNTHASE, the gene encoding the committed enzyme in the RFO biosynthetic pathway, has been documented to increase RFO amounts and to enhance plant survival of a variety of abiotic stresses. But the reason for the perceived improvement in stress tolerance is not currently known or even attributable to the accumulation of RFO. Using transposon interrupted raffinose synthase mutants of maize (Zea mays) we have established a positive correlation between the presence of raffinose and seed- seedling-vigor. This provides a new vantage point from which to evaluate the physiological function of the RFOs, a vantage point that has eluded plant scientists for over a century.  

M.D. Loiseau. "Sur une Nouvelle Substance Organique Cristallisée, Appellée Raffinose." Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. 1876/01 (82) 1058.