Proteomic analysis of leaf proteins during dehydration of the resurrection plant Xerophyta viscosa

Abstract

The desiccation-tolerant phenotype of angiosperm resurrection plants is thought to rely on the induction of protective mechanisms that maintain cellular integrity during water loss. Two-dimensional (2D) sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the Xerophyta viscosa Baker proteome was carried out during dehydration to identify proteins that may play a role in such mechanisms. Quantitative analysis revealed a greater number of changes in protein expression levels at 35% than at 65% relative water content (RWC) compared to fully hydrated plants, and 17 dehydrationresponsive proteins were identified by tandem mass spectrometry (MS). Proteins showing increased abundance during drying included an RNA-binding protein, chloroplast FtsH protease, glycolytic enzymes and antioxidants. A number of photosynthetic proteins declined sharply in abundance in X. viscosa at RWC below 65%, including four components of photosystem II (PSII), and Western blot analysis confirmed that two of these (psbP and Lhcb2) were not detectable at 30% RWC. These data confirm that poikilochlorophylly in X. viscosa involves the breakdown of photosynthetic proteins during dismantling of the thylakoid membranes. In contrast, levels of these photosynthetic proteins were largely maintained during dehydration in the homoiochlorophyllous species Craterostigma plantagineum Hochst, which does not dismantle thylakoid membranes on drying.

Photoprotection Conferred by Changes in Photosynthetic Protein Levels and Organization during Dehydration of a Homoiochlorophyllous Resurrection Plant

“…Together, these data suggest that, aside from the regulation of electron transport by modulation of the cytochrome b 6 f complex, some components of the system may be degraded. Elevated levels of the thylakoid protease FtsH have been observed at late stages of dehydration of the poikilochlorophyllous resurrection plant Xerophyta viscosa (Ingle et al, 2007), in which degradation of thylakoid proteins is a natural occurrence during desiccation. However, the observation of a similar phenomenon in homoiochlorophyllous types such as Selaginella tamariscina (Wang et al, 2010), H. rhodopensis (Georgieva et al, 2009;Sárvári et al, 2014), and Boea hygrometrica (Jiang et al, 2007) suggests .…”

A Systems‐Based Molecular Biology Analysis of Resurrection Plants for Crop and Forage Improvement in Arid Environments

“…This is a highly effective strategy to minimize ROS formation and this may explain why poikilochlorophyllous species appear to remain viable for longer periods than homoiochlorophyllous ones during desiccation [25]. The drawback of this strategy is that reassembly of the photosynthetic apparatus on rehydration requires coordinated transcription and de novo translation [26,28]. Hence, poikilochlorophyllous plants require much longer periods after rehydration to resume normal growth and development.…”

“…However, in all three studies, no protein identification was attempted. Recently, changes in the leaf proteomes of resurrection plants during desiccation were examined in X. viscose [28] and in B. hygrometrica [85] using quantitative 2D SDS-PAGE analysis. Several novel gene products, not previously isolated in transcriptomic studies, were identified as being upregulated during [61,86] T. ruralis cDNA libraries enriched with ESTs from slow drying and rehydrating gametophytes revealed genes involved in metabolic recovery, signaling, proteosomal processing, and splicing [94] Lycophyte Selaginella lepidophylla EST library corresponding to approximately 800 genes compared to 1300 genes from desiccation-sensitive S. moellendorfii.…”

“…Genes identified that are involved in transport, cytoskeleton, phenylpropanoid biosynthesis, LEA proteins, ELIPs, and HSPs [60] Angiosperm S. stapfianus 144 cDNA upregulated genes in dried leaves; mostly LEA genes, defense, and detoxification genes [95] X. humilis Normalized cDNA library (about 10 000 clones) from dried roots and leaves containing 424 sequenced and arrayed cDNA. Identification of LEA genes, antioxidant and signaling genes upregulated, and metabolism and growth genes downregulated [48] X. viscosa Identification of water stress-induced photosynthesisassociated proteins, chaperones, RNA-binding protein, 2-Cys peroxiredoxin, and protein phosphatase 2C [28] B. hygrometrica Water stress induces polypeptides involved in photosynthesis, glutathione metabolism, and phenolic metabolism [85] …”

“…In detached B. hygroscopica leaf tissue, dehydration-induced proteins include an ABC transporter and a vacuolar H þ -ATPase that may be involved in protection against osmotic stress, a glutathione peroxidase-like protein that may be involved in oxidative stress protection, and a polyphenol oxidase that may prevent proteolytic activity [85]. In severely dehydration-stressed X. viscosa leaf tissue (35% RWC), proteins that increase in abundance include a chloroplast FtsH protease, GDP-mannose-3 0 ,5 0 -epimerase, alcohol dehydrogenase, and protein phosphatase type 2C, VDAC1.1, and 2-cys peroxiredoxin that may be involved in antioxidant defense [28]. Of particular interest are proteins synthesized de novo upon dehydration (i.e., absent in hydrated tissues).…”