Suppression of the soybean phytoglobin GmPgb1 enhances tolerance to iron deficiency

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Asmundson, Bethany
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The effect of iron deficiency in soybean (Glycine max (L.) merr) seedlings over-expressing or down-regulating Glycine max Phytoglobin 1 (GmPgb1) was examined using an established hydroponic system which mimicked iron deficiency in soil. Iron deficient soybean plants down-regulating GmPgb1 displayed greater chlorophyll retention and decreased accumulation of reactive oxygen species relative to the GmPbg1 over-expressing and wild type (WT) plants. Suppression of GmPgb1 under iron deficiency conditions was also accompanied by elevated levels of ascorbic acid (ASC), and increased activities of catalase, superoxide dismutase and ASC recycling enzymes. When compared to WT and GmPgb1 over-expressing lines, iron deficient GmPgb1 suppressing plants also exhibited a higher Fe(II)/Fe(III) ratio. Pharmacological treatments altering the level of nitric oxide (NO) and ASC were further utilized to dissect the effects of GmPgb1 during iron deficiency. Applications of the NO donor, sodium nitroprusside (SNP), enhanced tolerance to iron deficiency by elevating the levels of ASC, the activities of several antioxidant enzymes, and the Fe(II)/Fe(III) ratio. A similar effect on this ratio was also observed when ASC was administered exogenously. Collectively this study reveals that suppression of GmPgb1 in soybean attenuates the effects of iron deficiency through changes in NO and antioxidant responses linked to the higher availability of Fe(II).
Iron deficiency, Phytoglobin, Ascorbic acid, Soybean, Nitric oxide, Glycine max