1. Mg 2+ uptake QTLs Hannah Itell and Eric Sawyer

2. 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

3. Biological roles for Mg 2+ ●vacuole: 3-13 mM Mg 2+ ●highest [Mg 2+ ]: thylakoid lumen (30- 50 mM), but importers unknown! ●Mg 2+ uptake hindered by acidic soils ●Mg 2+ deficiency can lead to Al 3+ toxicity; transporter competition chlorophyll a

4. Signs of Mg 2+ deficiency ●chlorophyll breakdown ●impaired sugar mobilization ●reduced growth, particularly roots

5. Mg 2+ biochemistry A.Cation channels B.MGT C.MHX D.Slow activating vacuolar channels (SVs) E.MGT5 F.MGT10 and FACCs (G) Bose et al. (2011)

6. 1. Mg 2+ channels (plasma membrane) ●Hyperpolarization-activated ●Depolarization-activated ●Voltage-independent ●Cyclic nucleotide-activated ●Non-selective ion channels ●AtCNGC10 (A. thaliana): mediates Mg 2+ mobilization through the plant

7. 2. Mg 2+ Carrier Proteins (MGTs) ●Magnesium (Mg 2+ ) Transport Family ●AtMGT1, 5, 7a, 9, 10 ●Vary in affinity and sensitivity to Al 3+ Plasma MembraneMitochondriaChloroplast

8. AtCNGC10AtMGT family Candidate gene BLAST results

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

10. C8 41,758,685 bp QTL: 40,141,039 +/- 1 Mbp 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

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

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

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

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 o vacuolar pumps/transporters o heavy metal transporters (Al 3+ -Mg 2+ antagonism?) o Ca 2+, Mg 2+, 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 Botany 62: 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 Ca 2+ fluxes in situ. Journal of Experimental Botany 59: 3845-3855.