Nodule-specific regulation of phosphatidylinositol transfer protein expression in Lotus japonicus

Phosphatidylinositol transfer proteins (PITPs) modulate signal transduction pathways and membrane-trafficking functions in eukaryotes. Here, we descri be the characterization of a gene family from Lotus japonicus that encodes a novel class of plant PITP-like proteins (LjPLPs) and that is regulated in an unusual nodule-specific manner, Members of this gene family were identi fied based on their nucleotide sequence homology with a previously describe d cDNA, LjNOD16, which encodes the L. japonicus late nodulin NIj16. NIj16 o r highly related amino acid sequences are shown to constitute C-terminal do mains of LjPLPs and are suggested to function as specific plasma membrane t argeting modules. The expression patterns of one member of this gene family (LjPLP-IV) revealed that LjNOD16 mRNA synthesis in nodules is the result o f the transcriptional activity of a nodule-specific promoter located in an intron of the LjPLP-IV gene. This intron-borne bidirectional promoter also generates nodule-specific antisense transcripts derived from the N-terminal PITP domain coding region of the LjPLP-IV gene. We propose that NIj16 prot ein synthesis and LjPLP-IV antisense transcript generation are components o f an elaborate mechanism designed to control LjPLP synthesis and/or functio ning in nodules.