Može li se C4 fotosinteza odvijati u jednoj stanici?

undergraduate thesis

• Title (english): Can C4 photosynthesis function within a single cell?
• Author: Ines Haberle
• Mentor: Mirta Tkalec (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2011, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Do nedavno, provođenje C4 fotosinteze povezivano je isključivo s biljkama koje imaju dva oblika fotosintetskih stanica, mezofilne stanice i stanice žilnog ovoja, odnosno Kranz anatomiju. Otkrićem tri vrste iz roda Chenopodiaceae, Bienertia cycloptera, Bienertia sinuspersici, i Suaeda aralocaspica, koje nemaju navedenih struktura, a ipak provode C4 fotosintezu, ustanovljeno je da je za C4 mehanizam dovoljna jedna stanica koja posjeduje dvije dobro odijeljene regije. Kod roda Bienertia to su periferni i centralni odjeljak, a kod roda Suaeda distalni i proksimalni odjeljak. Ovi odjeljci funkcionalno su analogni stanicama u Kranz anatomiji i omogućuju kompartimetizaciju organela, posebice dimorfnih kloroplasta te fotosintetskih enzima. Međutim smještaj dimorfnih kloroplasta kod ovih biljaka različit je nego kod biljaka s uobičajenom C4 fotosintezom što se objašnjava njihovom ulogom u zadovoljavanju energetskih potreba stanice. Za održavanje cjelokupne stanične organizacije odgovorni su elementi citoskeleta – guste mreže aktinskih niti i mikrotubula. Kontrola C4 ciklusa temelji se na regulaciji aktivnosti enzima fosfoenolpiruvat karboksilaze (PEPC). Ta regulacija može biti alosterička ili regulacija fosforilacijom. PEPC izoenzime nalazimo i kod C3 biljaka pa ovaj enzim ima veliku ulogu u utvrđivanju evolucije C4 biljaka. Uspoređivanjem PEPC izoenzima utvrđeno je da je C4 fotosinteza najvjerojatnije evoluirala iz C3 fotosinteze prije oko 25 – 32 milijuna godina. Zanimanje za C4 fotosintezu, osobito jednostaničnu, proizlazi iz činjenice da su biljke koje posjeduju ovaj mehanizam otpornije na ekstremne okolišne uvjete, pa bi njegova uspješna ugradnja u uobičajene C3 žitarice značile veliki napredak u svjetskom uzgoju usjeva.

Abstract (english)

Until recently, C4 photosynthesis was thought to be associated only with plants that possess two types of photosynthetic cells, mesophyll and bundle sheath cells, or so-called Kranz anatomy. The discovery of three Chenopodiaceae species, Bienertia cycloptera, Bienertia sinuspersici and Suaeda aralocaspica, which do not have these structures, and yet carry out C4 photosynthesis, showed that the C4 mechanism can be implemented within a single chlorenchyma cell that has two distinct regions. Those are peripheral and central compartments in Bienertia and distal and proximal compartments in Suaeda, respectively. Such cellular organisation is analogous to Kranz anatomy and enables compartmentalization of organelles, primarily dimorphic chloroplasts, as well as photosynthetic enzymes. A distinctive feature of the singlecell C4 photosynthesis is the positioning of dimorphic chloroplasts with respect to different compartments, which is the opposite than in common C4 plants. This is due to their role in meeting the energy requirements of the cell. The cytoskeleton, a dense network of actin filaments and microtubules, maintains the spatial organisation of cellular structures. The C4 cycle is controlled mainly through the regulation of activity of the enzyme phosphoenolpyruvate carboxylase (PEPC), either allosterically or via phosphorylation/dephosphorylation. Since PEPC isoenzymes are also found in C3 plants, they are important in elucidating the evolution of C4 plants. The comparison of these isoenzymes shows that the C4 plants probably evolved 25 – 32 million years ago from a C3 photosynthetic form. The fact that C4 plants have better photosynthetic performance on extreme habitats, such as deserts or saline soils, drives the interest for investigating single-cell C4 photosynthesis. Successful introduction of the C4 photosynthetic mechanism into C3 plants could mean a major breakthrough in the global crop cultivation.

• Keywords: C4 fotosinteza
• Keywords (english): C4 photosynthesis
• Language: croatian
• URN:NBN: urn:nbn:hr:217:068921
• Study programme: Title: Ecology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-04-06 07:52:21