Structural flexibility of a recombinant intrinsically disordered LEA protein from Ramonda serbica

Late embryogenesis abundant (LEA) proteins play a crucial role in the desiccation tolerance of resurrection plants, although their exact functions remain unclear. Therefore, we recombinantly produced desiccation-induced LEA4 protein member, RsLEAP30-His6, from Ramonda serbica and investigated its structural behaviour under simulated dehydration conditions. This is the first report on the production and purification of a recombinant LEA protein from the resurrection plant R. serbica. By immobilised metal affinity and size-exclusion chromatography, we successfully obtained RsLEAP30-His6 with a purity of over 95%, thus providing a robust and scalable method that can also be used for the production of other LEA proteins. Structural characterisation by circular dichroism spectroscopy in combination with in silico modelling, revealed that RsLEAP30 is predominantly disordered under fully hydrated conditions, whereas it adopts an α-helical structure under desiccation-like conditions and in the presence of a lipid mimetic. This disorder-to-order transition underpins the possible protective role of RsLEAP30 in chloroplasts, likely through interactions with thylakoids and desiccation-sensitive proteins enabling the rapid recovery of photosynthetic components upon rehydration. Our study provides new insights into the structure-function relationship of LEA proteins in desiccation tolerance and creates a basis for future bioengineering strategies to improve crop drought tolerance.