Plastid signal and the regulation of the tetrapyrrole biosynthesis

Abstract

In higher plants, nuclear-encoded genes related to the plastid-structure/function (e.g. Lhcb, RbcS) were co-coordinately regulated with the functional status of plastids. "Plastid signal" has been hypothesized for this regulatory mechanism. The analysis of gun mutants that have defects in this signaling has revealed the involvement of the tetrapyrrole intermediates (MgProtoIX) as a signaling factor. As oppose to the previous report, MgProtoIX level is 1/100 less accumulated than the control. However, we found that the synthesis of Proto-MgProtoXI-MgProtoIXMe are all elevated in the photobleached plants. Therefore, these intermediates are actively synthesized in the photobleached plants, but they are metablised and/or degraded immediately. We will report the comparison of tetrapyrrole synthesis capacity of gun mutants and discuss about the dynamics of the tetrapyrrole biosynthesis and the plastid signaling. We will also present the analysis of the new gun mutants.