QTL analysis of ferric reductase activity in the model legume lotus japonicus

Authors: Grusak, Michael

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2010
Publication Date: 6/26/2010
Citation: Grusak, M.A. 2010. QTL analysis of ferric reductase activity in the model legume lotus japonicus [Abstract]. 15th International Symposium on Iron Nutrition and Interactions in Plants. p. 105.

Interpretive Summary:

Technical Abstract: Physiological and molecular studies have demonstrated that iron accumulation from the soil into Strategy I plants can be limited by ferric reductase activity. An initial study of Lotus japonicus ecotypes Miyakojima MG-20 and Gifu B-129 identified significant leaf chlorosis and ferric reductase activity differences when these lines were grown under iron limited conditions. In order to determine the genetic basis underlying these differing responses to low iron conditions, Miyakojima and Gifu derived recombinant inbred (RI) lines were grown hydroponically with iron (5 uM Fe[III]EDDHA) for 35 d, then were transferred to low iron growth media (0.5 uM Fe[III]EDDHA) for 7 d. Replicate RI lines were then tested for leaf chlorosis and whole root ferric reductase activity. QTL analysis was conducted using community provided genetic maps. For both traits examined in this study, a single quantitative trait locus (QTL) was identified. The ferric reductase activity QTL explained 32.1% of the variation seen across the RI population while the leaf chlorosis QTL explained 28.9% of the variation. Both QTLs overlap a 5.8 cM region of chromosome 3. A root specific, iron deficiency induced ferric reductase gene (LjFRO1) was cloned and sequenced from both parental lines. LjFRO1 mapped to the same genetic region as the leaf chlorosis and ferric reductase QTLs. Transcript abundance differences in LjFRO1 expression were identified between the two ecotypes. LjFRO1 proteins from both ecotypes were examined by functional yeast assays and were shown to donfer iron reductse activity. In our presentation, we will discuss the role that ecotypic variation can play in ferric reductase capacity and whole plant iron nutrition. We also will discuss the relevance of model legume data towards crop improvement in agronomic legumes.