Plant Physiol, November 2000, Vol. 124, pp. 1427-1436

Protein Dynamics in Thylakoids of the Desiccation-Tolerant Plant Boea hygroscopica during Dehydration and Rehydration¹

Dipartimento di Chimica e Biotecnologie Agrarie, Università di Pisa, Via del Borghetto, 80, I-56124 Pisa, Italy (F.N.-I., M.F.Q., C.L.M.S.); Istituto di Chimica Quantistica ed Energetica Molecolare, Consiglio Nazionale delle Ricerche, Via Alfieri, 1, I-56010 Ghezzano, Italy (C.P.); Dipartimento di Biologia, Università di Padova, Via Trieste, 75, I-35121 Padova, Italy (N.R.); and Dipartimento di Agronomia e Produzioni Erbacee, Università di Firenze, Piazzale delle Cascine 18, I-50144 Firenze, Italy (C.V.)

Plants of Boea hygroscopica F. Muell were dehydrated to 9% relative water content (RWC) by withholding water for 26 d, and afterward the plants were rehydrated. Leaves were taken from control plants after 7, 12, and 26 d from the beginning of dehydration, and after 6 and 48 h from rehydration. The RWC decreased by 80% during dehydration, but the leaves regained RWC with rehydration. Dehydrated plants showed lesser amounts of proteins, lipids, and chlorophyll, all of which increased following rewatering. The lipid-to-protein ratio, which decreased during dehydration, returned to control level after 48 h of rehydration. Thylakoid lipids were more unsaturated when RWC reached the value of 9%. EPR measurements of spin-labeled proteins showed the presence of three different groups of proteins with different mobility in thylakoid membranes. The rotational correlation time of groups 1 and 2 increased with dehydration and decreased upon rehydration, whereas group 3 showed little changes. Desiccation did not cause thylakoid swelling or breakage, but the membrane system assemblage showed changes in thylakoid stacking. After 48 h of rehydration the membrane system recovered completely the organization of the fully hydrated state, showing several well-defined and regularly distributed grana.