1a.Objectives (from AD-416):
Make transgenic soybeans that have altered expression of soybean genes involved in iron acquisition and assess growth of transgenic and control plants under iron-sufficient and iron-deficient conditions.
1b.Approach (from AD-416):
A BetaHLH transcription factor controlling iron signaling (Glyma 03g28610) has been identified in the introgressed region on chromosome 3 of soybean which regulates iron deficiency chlorosis. This gene has striking similarity to the iron transcriptional regulator POPEYE gene of Arabidopsis. The soybean Glyma 03g28610 has been identified in several soybean populations showing resistance to iron deficiency chlorosis. Transgenic soybeans will be generated that have reduced expression of Glyma 03g28610. Growth of transgenic and control plants under iron sufficient and iron deficient conditions will be assessed. In addition, use already transformed soybean to modify expression of the iron chelator NAS (nicotamine synthase). Overexpression of NAS in rice has increased iron accumulation. Modify NAS expression in soybean to see if it will modify the iron deficiency chlorosis response. Grow plants from T0 seed and use to analyze T1 generation for response to iron.
Grow these plants to maturity and characterize the transgenic plants using molecular biology techniques to estimate the number of copies of transgenes inserted into these lines. Grow progeny seed from these lines in Fe sufficient and insufficient conditions to assess the effect of these genes on iron metabolism. Characterize the expression of other genes involved in iron metabolism to determine if they are also affected by the insertion and overexpression of these specific iron genes.
Transgenic plants that overproduce a transcript for a bHLH transcription factor designated a POPEYE have been developed and the T2 generation of seed is being produced. Transgenic plants over-producing a transcript for nodule malate dehydrogenase (MDH) were analyzed. One of the lines over-producing nodule MDH had increased total nitrogen as compared to the controls.