Mechanism and biological function of the regulation of cellulose synthesis by light
Zusammenfassung der Projektergebnisse
In this study I aimed to analyse light regulation of cellulose biosynthesis and its importance for the development in the model plant Arabidopsis thaliana. The cellulose synthase complex (CSC) produces cellulose in Arabidopsis and is composed of several cellulose synthase (CESA) subunits. The exact arrangement of CESAs within the complex is not yet known. However, it is clear that CESA1, 3 and 6 are members of the CSC, but only CESA1 and 3 are essential for its functionality. CESA6 most likely can be replaced by one of its close relatives, CESA2 and CESA5. Our data suggests that, in dark conditions, CESA5 is present in active complexes with CESA6 and CESA3 at the top of the hypocotyl where a very thick cell wall is deposited; in later stages CESA5 becomes excluded from active CSCs. In the WT, CESA5-containing CSCs (C5cCSC) are motile in dark and light conditions. The Arabidopsis cesa6 mutant has strong phenotypes only in dark but not in light conditions. In light growth, C5cCSC are always motile. We found in this study that in the dark-grown cesa6 mutant most C5cCSCs are immobile due to a CESA5-interaction with microtubule (MT). Depolymerization of MT resulted in an acceleration of these formerly immobile C5cCSCs. In addition, our results show that in absence of CESA6, only CSCs containing a phosphorylated version of CESA5 were motile in the dark. Those CSC containing a dephosphorylated version remained immobile. Our results indicate that the phosphorylation state of CESA5 might influence the strength of the CESA5-connection to MT. Our results based on spinning disk confocal microscopy data show that flushes with red-, but not far-red light could induce motility of C5cCSCs in dark-grown cesa6 mutants. Red flushes had no effect anymore on CESA5 motility in a double mutant phytochromeB/cesa6. We hypothesize that phytochrome photoreceptors perceive light signals and transfer them via unknown signalling components to the C5cCSCs. Following our hypothesis, CESA5 then most likely is phosphorylated, the direct or indirect interaction of CESA5 and microtubule is released and C5cCSC become motile. Due to the fact that the importance of phosphorylation and connection to MT on motility of C5cCSCs is only evident in visible of CESA6, we hypothesize that in dark wild-type conditions a pool of phosphorylated and unphosphorylated CESA5 might exist, CSCs containing the latter are immobile but are most likely hidden by motile CSCs containing phosphorylated CESA5. All together, our data suggest for an involvement of CESA5 in light-dependent fine-tuning of cellulose deposition in specific parts of the Arabidopsis hypocotyl.
Projektbezogene Publikationen (Auswahl)
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2010. A role for pectin de-methylesterification in a developmentally-1 regulated growth acceleration in dark-grown Arabidopsis hypocotyls. New Phytologist, 188:726-39
Pelletier S, Van Orden J, Wolf S, Vissenberg K, Delacourt J, Assoumou Ndong Y, Pelloux J, Bischoff V, Urbain A, Mouille G, Lemonnier G, Renou JP Höfte H
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2010. Involvement of TBL / DUF231 Proteins into Cell Wall Biology. Plant Signal & Behavior, 5: 1057-1059
Bischoff V, Selbig J, Scheible WR
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2011. CESA5 is Required for the Synthesis of Cellulose with a Role in Structuring the Adherent Mucilage of Arabidopsis Seeds. Plant Physiology, 156:1725-39
Sullivan JS, Ralet MC, Berger A, Diatloff E, Bischoff V, Gonneau M, Poll AM, North HM
