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Mg 2+ uptake QTLs

Mg 2+ uptake QTLs. Hannah Itell and Eric Sawyer. Biological roles for Mg 2+. chlorophyll common cofactor (RNA pol, kinases, ATPases, …) most Mg 2+ is not free in cytoplasm (ATP/nucleotide-chelated or in organelles) < 2 mM. chlorophyll a. Biological roles for Mg 2+.

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Mg 2+ uptake QTLs

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  1. Mg2+ uptake QTLs Hannah Itell and Eric Sawyer

  2. Biological roles for Mg2+ • chlorophyll • common cofactor (RNA pol, kinases, ATPases, …) • most Mg2+ is not free in cytoplasm (ATP/nucleotide-chelated or in organelles) < 2 mM chlorophyll a

  3. Biological roles for Mg2+ • vacuole: 3-13 mM Mg2+ • highest [Mg2+]: thylakoid lumen (30-50 mM), but importers unknown! • Mg2+ uptake hindered by acidic soils • Mg2+ deficiency can lead to Al3+ toxicity; transporter competition chlorophyll a

  4. Signs of Mg2+ deficiency • chlorophyll breakdown • impaired sugarmobilization • reduced growth, particularly roots

  5. Mg2+ biochemistry • Cation channels • MGT • MHX • Slow activating vacuolar channels (SVs) • MGT5 • MGT10 and FACCs (G) Bose et al. (2011)

  6. 1. Mg2+ channels (plasma membrane) • Hyperpolarization-activated • Depolarization-activated • Voltage-independent • Cyclic nucleotide-activated • Non-selective ion channels • AtCNGC10 (A. thaliana): mediates Mg2+ mobilization through the plant

  7. 2. Mg2+ Carrier Proteins (MGTs) • Magnesium (Mg2+) Transport Family • AtMGT1, 5, 7a, 9, 10 • Vary in affinity and sensitivity to Al3+ Plasma Membrane Mitochondria Chloroplast

  8. Candidate gene BLAST results AtCNGC10 AtMGT family

  9. IGB QTL: 7,628,656 +/- 1 Mbp No hits :( C6 39,822,476 bp

  10. IGB Cation/Calcium Exchanger @ 39,717,422 Cation/H+ Exchanger @ 39,945,936 Cation/H+ Exchanger @ 39,950,514 Cation/H+ Antiporter @ 40,277,578 QTL: 40,141,039 +/- 1 Mbp C8 41,758,685 bp

  11. IGB Metallothionein-like protein @ 43,295,039 Golgi-assoc. cation binding protein Heavy metal transport/detoxification domain-containing protein @ 43,792,027 Calmodulin-like protein @ 43,857,726 Calcium transporting ATPase @ 43,882,735 Similar to AT1G07810 cation transporter Heavy metal transport/detoxification superfamily protein @ 44,678,689 QTL: 44,023,210 +/- 1 Mbp C5 46,902,585 bp

  12. IGB V-type proton ATPase subunit d2 @ 35,255,037 Caleosin-related family protein @ 35,570,359 Major facilitator superfamily protein @ 35,825,037 small solute transporter Heavy metal transport/detoxification superfamily protein @ 36,474,786 Cation transport regulator-like protein @ 36,606,567 QTL: 35,691,416 +/- 1 Mbp Vacuolar cation/proton exchanger @ 39,433,988 & 39,437,869 QTL: 39,973,848 +/- 1 Mbp V-type proton ATPase 16 kDa proteolipid subunit c1/c3/c5 @ 39,793,003 C7 48,366,697 bp Cation proton exchanger @ 39,509,003 Heavy metal transport/detoxification superfamily protein @ 40,122,906

  13. IGB Magnesium Transporter (Predicted) @ 39,807,316 Mitochondrial Carrier Protein @ 40,692,677 QTL: 40,219,218 +/- 1 Mbp C4 53,719,093 bp

  14. Conclusions • No candidate gene BLAST hits within 1 Mbp of QTL • CNGC10 and MGT family hit every QTL +/- 10 Mbp • IGB search within 1 Mbp of QTLs found • vacuolar pumps/transporters • heavy metal transporters (Al3+-Mg2+ antagonism?) • Ca2+, Mg2+, and general cation transporters and binding proteins

  15. References Bose, J. et al. 2010. Role of magnesium in alleviation of aluminium toxicity in plants. Journal of Experimental Botany62: 2251-2264. Hermans, C. et al. 2010. Systems analysis of the responses to long-term magnesium deficiency and restoration in Arabidopsis thaliana. New Phytologist 187: 132-144. Perez, V. et al. 2008. Homeostatic control of slow vacuolar channels by luminal cations and evaluation of the channel-mediated tonoplast Ca2+ fluxes in situ. Journal of Experimental Botany 59: 3845-3855.

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