|Budget Amount *help
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2001: ¥2,200,000 (Direct Cost: ¥2,200,000)
A potexvirus (SMYEPV), which is a causal agent of mild yellow edge disease in strawbernes, is restricted the distribution to phloem cells unlike the other potexviruses. I hypothesized that the expression of triple gene block protein 1 (TGBp1) that is involved in cell to-cell movement of the virus relates to the limited distribution. First, the genome of Japanese S2-1 isolate was completely sequenced. At least two types A and B were found in the sequences, suggesting the diversity of SMYEPV genom. The nucleotide sequences of A-type and B-type share 83% identity, and shows 85% or 82% identity with that of MY-18 isolate in USA reported, respectively. Both sequences lack an AUG initiation codon for the putative ORF 2 encoding the TGBp1, strongly suggesting a non-AUG initiation for translation of the TGBp1. Next, an initiation codon for the putative ORF 2 was analyzed by in vitro translation system using in vitro transcripts of the wild-type and mutant sequences. The results revealed that the translation of TGBp1 is not initiated by an AUG but a CUG codon. The efficiency of translation by a CUG initiation is obviously lower than that by an AUG initiation. The results indicate that SMYEPV multiplicated in phloem cells probably can not generally move to neighbor cells because of the insufficiently translation of TGBp1.
It is predicted on the hypothesis that the multiplication of SMYEPV extends to mesophyll cells by AUG initiation for the TGBp1 translation. To examine the prospect, the infectious cDNA clone to monitor the replication of SMYEPV was tried to construct. The full-length cDNA was constructed by linking the B-type cDNA fragments together. In addition, CaMV 35S promoter and CaMV terminator were linked to the full-length cDNA. The foundamation of monitor system for the SMYEPV replication using the infectious cDNA clone was laid in this study.