Proteomic analysis of the response to high-salinity stress in Physcomitrella patens

Abstract

Physcomitrella patens is well known because of its importance in the study of plant systematics and evolution. The tolerance of P. patens for high-salinity environments also makes it an ideal candidate for studying the molecular mechanisms by which plants respond to salinity stresses. We measured changes in the proteome of P. patens gametophores that were exposed to high-salinity (250, 300, and 350 mM NaCl) using two-dimensional gel electrophoresis (2-DE) via liquid chromatography-tandem mass spectrometry (LC-MS/MS). Sixty-five protein spots were significantly altered by exposure to the high-salinity environment. Among them, 16 protein spots were down-regulated and 49 protein spots were up-regulated. These proteins were associated with a variety of functions, including energy and material metabolism, protein synthesis and degradation, cell defense, cell growth/division, transport, signal transduction, and transposons. Specifically, the up-regulated proteins were primarily involved in defense, protein folding, and ionic homeostasis. In summary, we outline several novel insights into the response of P. patens to high-salinity; (1) HSP70 is likely to play a significant role in protecting proteins from denaturation and degradation during salinity stress, (2) signaling proteins, such as 14-3-3 and phototropin, may work cooperatively to regulate plasma membrane H(+)-ATPase and maintain ion homeostasis, (3) an increase in photosynthetic activity may contribute to salinity tolerance, and (4) ROS scavengers were up-regulated suggesting that the antioxidative system may play a crucial role in protecting cells from oxidative damage following exposure to salinity stress in P. patens.

Exploring the Mechanism of Physcomitrella patens Desiccation Tolerance through a Proteomic Strategy

“…All 71 differentially displayed protein spots were excised from preparative 2-D gels, digested with trypsin, and analyzed through LC-MS/ MS. We searched the amino acid sequences against the databases using the SEQEST software as described before (Wang et al, 2008). All of the differentially expressed proteins could be identified, with just 19 of them categorized as unknown or putative proteins (Table I), and their sequence-matched peptides are shown in Supplemental Table S1.…”

“…We detected HSP70s as the major HSPs that play a role in the P. patens response to desiccation (Table I) and cold (data not shown). Recently, these proteins have also been shown to be important for high salinity (Wang et al, 2008). Genome analysis has shown that the HSP70 family has expanded to nine cytosolic members in P. patens, whereas all algal genomes sequenced to date encode a single cytosolic HSP70 (Wang et al, 2004).…”

Responses and tolerance to salt stress in bryophytes

“…These proteins are phototropin, myelin basic protein kinase, MCamb1 and MCamb2, 14-3-3 like protein and PpDBF1. [4][5][6][7] Phototropin is the blue light receptor that mediates phototropism, chloroplast relocation and stomatal opening in higher plants. 8 In Physcomitrell patens, phototropin and 14-3-3 proteins may work cooperatively to regulate plasma membrane H + -ATPase and maintain ion homeostasis.…”

“…8 In Physcomitrell patens, phototropin and 14-3-3 proteins may work cooperatively to regulate plasma membrane H + -ATPase and maintain ion homeostasis. 4 The 14-3-3 proteins are important eukaryotic regulatory proteins, most of which are involved in cellular signaling pathways. 9 Through regulating the activities of kinases and phosphatase, 14-3-3 proteins integrate themselves into several levels of signal transduction cascades.…”

“…Ion homeostasis in salt environments of bryophytes is dependent on transmembrane transport proteins that mediate ion fluxes, including sodium ATPase (PpENA1 and PpENA2), vacuolar H + -ATPase, PpSHP1 and PpSHP2, chloride channel protein and ABC transporters. 4,[16][17][18] Na + competes with K + for intracellular influx because these cations are transported by common proteins. 19,20 During exposure to salt environments, the maintenance of K + and Na + homeostasis is crucial in organisms.…”