Chao_etal_TSC10A_mapping

ABSTRACT: Sphingolipid synthesis is initiated by condensation of serine with palmitoyl-CoA to produce 3-ketodihydrosphinganine (3-KDS), which is subsequently reduced by a 3-KDS reductase to dihydrosphinganine (DHS). Serine palmitoyltransferase was recently shown to be essential for plant viability, but the 3-KDS reductase step of sphingolipid synthesis has not been investigated in plants. Arabidopsis thaliana contains two genes (At3g06060/TSC10A and At5g19200/TSC10B) that encode proteins with significant homology to the yeast 3-KDS reductase, Tsc10p. Heterologous expression, in yeast, of either A. thaliana gene restored 3-KDS reductase activity to the yeast tsc10Δ mutant, thereby identifying both as bona fide 3-KDS reductase genes. Consistent with previous evidence that sphingolipids have essential functions in plants, double mutant progeny lacking both genes were not recovered. Although the 3-KDS reductase genes are functionally redundant and ubiquitously expressed in A. thaliana, 3-KDS reductase activity was reduced to approximately 10% of wild-type levels in the loss-of-function tsc10a mutant, leading to an altered sphingolipid profile compared to wild-type plants. Interestingly, this perturbation of sphingolipid biosynthesis in the A. thaliana tsc10a mutant leads to significant alterations in the leaf ionome, including increases in Na, K and Rb (a K analogue), and decreases in Mg, Ca, Fe, and Mo. Reciprocal grafting revealed that these changes in the leaf ionome are driven by the root, and are associated with both increases in root suberin, and elevation of expression in the root of genes involved in Fe homoeostasis, including the Fe-transporter IRT1. Keywords: genomic hybridization bulked segregant analysis Overall design: Hybridizations from a set of Bulk Segregant analysis. An F2 population from 7113 in the col-0 background crossed to Ler-0 was analyzed. This series contains the 3 hybs from Ler used to identify Single Feature Polymorphisms, the 3 hybs of Col-0 they were compared to, and 1 hyb for each pool from the BSA mapping(low Ca/Mg Pool and wild type pools).