Desiccation‐induced alterations in surface topography of thylakoids from resurrection plant Haberlea rhodopensis studied by atomic force microscopy, electrokinetic and optical measurements

Abstract

With their ability to survive complete desiccation, resurrection plants are a suitable model system for studying the mechanisms of drought tolerance. In the present study, we investigated desiccation-induced alterations in surface topography of thylakoids isolated from well-hydrated, moderately dehydrated, severely desiccated and rehydrated Haberlea rhodopensis plants by means of atomic force microscopy (AFM), electrokinetic and optical measurements. According to our knowledge, so far, there were no reports on the characterization of surface topography and polydispersity of thylakoid membranes from resurrection plants using AFM and dynamic light scattering. To study the physicochemical properties of thylakoids from well-hydrated H. rhodopensis plants, we used spinach thylakoids for comparison as a classical model from higher plants. The thylakoids from well-hydrated H. rhodopensis had a grainy surface, significantly different from the well-structured spinach thylakoids with distinct grana and lamella, they had twice smaller cross-sectional area and were 1.5 times less voluminous than that of spinach. Significant differences in their physicochemical properties were observed. The dehydration and subsequent rehydration of plants affected the size, shape, morphology, roughness and therefore the structure of the studied thylakoids. Drought resulted in significant enhancement of negative charges on the outer surface of thylakoid membranes which correlated with the increased roughness of thylakoid surface. This enhancement in surface charge density could be due to the partial unstacking of thylakoids exposing more negatively charged groups from protein complexes on the membrane surface that prevent from possible aggregation upon drought stress.

Protein Changes in Shade and Sun Haberlea rhodopensis Leaves during Dehydration at Optimal and Low Temperatures

“…Phosphoenolpyruvate, however, is also a precursor in the biosynthesis of phenolics in the chloroplasts [ 55 ]. Since the accumulation of phenolic compounds in the thylakoid lumen is significant during desiccation [ 25 , 56 ], at least a part of phosphoenolpyruvate biosynthesis is directed towards the chloroplast accumulation of phenolics. Besides cytoplasmic carbohydrate metabolism enzymes, the induction of the cell wall UDP-D-apiose/UDP-xylose synthase was also detected, which is similar to the results of Mladenov et al [ 35 ].…”

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“…The thylakoid membrane was suspended in buffer C (100 mM sucrose, 10 mM Hepes-NaOH, 5 mM NaCl, 10 mM NaF, 10 mM MgCl 2 , pH 7.5), frozen with liquid nitrogen and stored at À80 C until use. Imaging of isolated thylakoids was accomplished with AFM according to published procedures (Doltchinkova et al, 2019). The thylakoid volume was calculated based on the formula V ¼ (4pabh)/3, where a, b and h were the length, width and the height of the thylakoid, respectively (Doltchinkova et al, 2019).…”

“…Imaging of isolated thylakoids was accomplished with AFM according to published procedures (Doltchinkova et al, 2019). The thylakoid volume was calculated based on the formula V ¼ (4pabh)/3, where a, b and h were the length, width and the height of the thylakoid, respectively (Doltchinkova et al, 2019).…”