Reactivation of the Photosynthetic Apparatus of Resurrection Plant <i>Haberlea rhodopensis</i> during the Early Phase of Recovery from Drought- and Freezing-Induced Desiccation
Gergana Mihailova | Nikolai K. Christov | Éva Sárvári | Ádám Solti | Richard Hembrom | Katalin Solymosi | Áron Keresztes | Maya Velitchkova | Antoaneta V. Popova | Lyudmila Simova-Stoilova | Elena Todorovska | Katya Georgieva
<i>Haberlea rhodopensis</i> is a unique desiccation-tolerant angiosperm that also survives winter frost. As, upon freezing temperatures, <i>H. rhodopensis</i> desiccates, the taxon is proposed to survive low temperature stress using its desiccation tolerance mechanisms. To reveal the validity of this hypothesis, we analyzed the structural alterations and organization of photosynthetic apparatus during the first hours of recovery after drought- and freezing-induced desiccation. The dynamics of the ultrastructure remodeling in the mesophyll cells and the restoration of the thylakoid membranes shared similarities independent of the reason for desiccation. Among the most obvious changes in thylakoid complexes, the proportion of the PSI-LHCII complex strongly increased around 70% relative water content (RWC), whereas the proportion of Lhc monomers decreased from the beginning of rehydration. We identified enhanced levels of cyt <i>b<sub>6</sub>f</i> complex proteins that contributed to the enhanced electron flow. The high abundance of proteins related to excitation energy dissipation, PsbS, Lhcb5, Lhcb6 and ELIPs, together with the increased content of dehydrins contributed to the preservation of cellular integrity. <i>ELIP</i> expression was maintained at high levels up to 9 h into recovery. Although the recovery processes from drought- and freezing-induced desiccation were found to be similar in progress and time scale, slight variations indicate that they are not identical.
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