MSGID: 1:317/3 6270b028   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Lighting the tunnel of plant evolution: Scientists explore importance of   
   two-pore channels in plants    
      
     Date:   
         May 2, 2022   
     Source:   
         Tokyo University of Science   
     Summary:   
         Two-pore ion channels are present in many eukaryotes -- both   
         animals and plants. While the possible involvement of these   
         channels in environmental stress responses have been discussed in   
         higher plants, their localizations and functional significance   
         remain largely unknown. Now, researchers have found the missing   
         pieces of evolutionary history of two- pore channels in a species   
         of liverwort.   
      
      
      
   FULL STORY   
   ==========================================================================   
   Two-pore channels (TPCs) are ancient ion channels present in the cells   
   of both animals and plants. In animals, including humans, these ion   
   channels play important roles in biological activities in various tissues,   
   such as in the brain and nervous system. All land plant species contain   
   TPC genes; in many higher vascular plants such as Arabidopsis thaliana   
   (Arabidopsis) and Oryza sativa(rice), a single TPC gene is involved in   
   the activity of slow vacuolar (SV) channels (voltage-dependent cation   
   channels) along with long-distance signalling, defence, and responses to   
   environmental stress. However, very little is known about the function   
   of TPC proteins in non-flowering mosses and liverworts-some of the oldest   
   organisms on Earth.   
      
      
   ==========================================================================   
   In a recent study, a team of researchers led by Prof. Kazuyuki   
   Kuchitsu from Tokyo University of Science, Japan, collaborated with   
   researchers from Maria Curie-Sklodowska University, Poland, to explore   
   the evolutionary and physiological significance of two-pore channels   
   in the non-flowering bryophyte Marchantia polymorpha. Their widely   
   recognized and appreciated article, which discusses this study in detail,   
   was first published online in December 2021 and subsequently in print in   
   the February issue in Plant and Cell Physiology. The article has also   
   been chosen as an "Editor's Choice" and "Research Highlight" article   
   for the journal, which has published a commentary.   
      
   M. polymorpha, or common liverwort, grows as thin, flat green sheets on   
   moist soil or rock, and is an extant descended from one of the earliest   
   plants to colonize land. M. polymorpha is a simple model organism that   
   has been used to analyze the common characteristics of land plants. ''We   
   realized that the genome of M. polymorpha has three TPC homologs: MpTPC1,   
   2, and 3, belonging to two distinctive groups, type 1 and type 2 TPC   
   genes. We aimed to know what these two subgroups of TPC proteins do in   
   M. polymorpha,'' Prof. Kuchitsu explains.   
      
   To do so, the researchers first performed a phylogenetic analysis of the   
   TPC genes in the green plant lineage. Then they characterized the three   
   TPC proteins: MpTPC1 from the Type 1 TPC gene and MpTPC2 and MpTPC3 from   
   the Type 2 TPC gene. Tagging these proteins with a fluorescent marker,   
   they studied their localization in M. polymorpha cells. By CRISPR-Cas9   
   genome editing, the researchers developed mutant plants that didn't   
   contain functional TPC1, TPC2, or TPC3 genes and double mutant plants   
   that lack functions of both TPC2 and TPC3 genes. Then, by patch-clamp   
   electrophysiology analyses, they measured the ionic currents in isolated   
   vacuoles from the living cells of M. polymorpha plants.   
      
   The results of the phylogenetic analyses provided some intriguing insights   
   into the evolutionary history of M. polymorpha. "Unlike the type 1 TPC   
   gene, which is well conserved in all land plants, type 2 TPCs were found   
   in algal species.   
      
   This suggested that although the type 2 TPCs emerged before plants   
   colonized the land, they failed to make their way into the genome of   
   higher vascular plants and hornworts," Prof. Kuchitsu tells us.   
      
   The researchers also found that the three TPC proteins were primarily   
   localized at the vacuolar membrane of M. polymorpha. The mutant that   
   lacked a functional TPC1 gene showed no SV channel activity. But mutants   
   that lacked either functional TPC2, TPC3, or both, exhibited usual SV   
   channel activity. Molecules such as phosphatidylinositol-3,5-bisphosphate   
   and nicotinic acid adenine dinucleotide phosphate, that activate the   
   TPCs of mammalian cells, failed to affect the ion channel activity in   
   isolated vacuoles of the mutant plants.   
      
   Prof. Kuchitsu surmises, "These observations, when tied down together,   
   indicated that the type 1 TPCs-which are ubiquitous in all land plant   
   species- are responsible for SV channels in their vacuolar membrane,   
   but the type 2 TPCs likely encode ion channels that are different from   
   the SV channel and animal TPCs."  The team's findings provide much-needed   
   functional and evolutionary insights into the important-yet-elusive TPC   
   family in plants, and on plant ion channels in general. With their eye   
   on future research, they also aim to use insights from the evolutionary   
   history of plants for improving plant growth and defence mechanisms   
   against biotic and abiotic stresses. This could benefit industries like   
   agriculture, among others.   
      
   The funding for this research was obtained through a grant from Japanese   
   Society for the Promotion of Science and the National Science Centre,   
   Poland.   
      
      
   ==========================================================================   
   Story Source: Materials provided by Tokyo_University_of_Science. Note:   
   Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Kenji Hashimoto, Mateusz Koselski, Shoko Tsuboyama, Halina   
      Dziubinska,   
         Kazimierz Trębacz, Kazuyuki Kuchitsu. Functional Analyses of   
         the Two Distinctive Types of Two-Pore Channels and the Slow Vacuolar   
         Channel in Marchantia polymorpha. Plant and Cell Physiology, 2022;   
         63 (2): 163 DOI: 10.1093/pcp/pcab176   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220502094736.htm   
      
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