The Waxy (Wx) protein has been identified as granule-bound starch synthase (GBSS; EC 24.1.21), which is involved in amylose synthesis in plants. Although common wheat (Triticum aestivum L.) has three Wx proteins, "partial waxy mutants" lacking one or two of the three proteins have been found. Using such partial waxy mutants, tetra- and hexaploid waxy mutants with endosperms that are stained red-brown by iodine were produced. Both mutants showed loss of Wx protein and amylose. This is the first demonstration of genetic modification of wheat starch.

Nullisomic analysis of waxy (Wx) protein of hexaploid wheat (Triticum aestivum L.) cv. "Chinese Spring" using two-dimensional polyacrylamide gel electrophoresis revealed that three Wx loci, Wx-A1, Wx-B1, and Wx-D1, located on chromosome arms 7AS, 4AL, and 7DS, produce three distinct Wx subunit groups, subunit group-A (SGA), SGB, and SGD, respectively. SGA has a higher molecular weight and a more basic isoelectric point (pI) than the other two. SGB and SGD have the same molecular weight but a slightly different pI range. Owing to the detection of these three subunit groups, we were able to identify the expression of three waxy genes in wheat endosperm and to find two types of mutants among Japanese wheat cultivars, one lacking SGA and the others SGB. These results suggest the possibility of breeding a waxy wheat.

Two cultivars with a low amylose content, Kanto107 (K107) and K79, were discovered in Japanese common wheat (Triticum aestivum L.). The amount of Wx protein, identified as a single major starch granule‐bound protein of about 61 kD by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE), was greatly decreased in those two cultivars. Analysis of their Wx protein with a modified SDS‐PAGE and two dimensional‐PAGE showed that two of the three Wx proteins, produced by Wx‐A1 and Wx‐B1 loci, were not detected. It was thus concluded that only one locus, Wx‐D1, was active in the two low amylose cultivars. These mutants were termed “partial waxy mutants” and considered to be very useful material for breeding waxy wheat.

The complete nucleotide sequence of the genomic RNA of cucumber green mottle mosaic virus watermelon strain SH (CGMMV-SH) was determined using cloned cDNA. This sequence is 6421 nucleotides long containing at least four open reading frames, which correspond to 186K, 129K, 29K and 17.3K proteins. The 17.3K protein is the coat protein. Sequence analysis shows that CGMMV-SH is very closely related to another watermelon strain, CGMMV-W, although three amino acid substitutions in the 29K protein were found between these strains. The sequence was also compared to those of other tobamoviruses, tobacco mosaic virus (TMV) vulgare, TMV-L (a tomato strain) and tobacco mild green mosaic virus reported by other groups. It shows 55 to 56% identity with these viruses. The size and location of the open reading frames are very similar to those of TMV but the 129K and 186K proteins are composed of 1142 and 1646 amino acids, being larger than those of TMV by 27 and 31 amino acids, respectively. The deduced amino acid sequences of these proteins are highly homologous to those of TMV, especially in the readthrough downstream region of the 186K protein.

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In an attempt to generate soybean plants resistant to soybean dwarf virus (SbDV), we transformed a construct containing inverted repeat-SbDV coat protein (CP) genes spaced by beta-glucuronidase (GUS) sequences into soybean somatic embryos via microprojectile bombardment. Three T(0) plants with an introduced CP gene were obtained, and one generated T(1) seeds. The presence of the transgene in T(1) plants was confirmed by PCR and Southern blot hybridization analysis, but expression of CP was not detected by northern blot hybridization analysis. Two months after inoculation of SbDV by aphid, T(2) plants contained little SbDV-specific RNA and remained symptomless. These plants contained SbDV-CP-specific siRNA. These results suggest that the T(2) plants achieved resistance to SbDV by an RNA-silencing-mediated process.

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Complementary and genomic DNA clones coding for aldolase C-1, the fourth-type isozyme of aldolase in rice Oryza sativa L., have been characterized. The organization of the gene is quite similar to those encoding rice aldolase C-a and a maize cytoplasmic-type aldolase, in that introns are located in the same position. Amino acid sequences are highly conserved among cytoplasmic aldolases in plants. Expression of the gene in rice callus is activated by a protein phosphatase inhibitor okadaic acid, and is inhibited in the presence of thapsigargin, a reagent which increases calcium influx into the cytoplasm. The inhibition is rescued by the simultaneous addition of protein kinase inhibitor H-7. Thus, it is suggested that expression of the aldolase C-1 gene is regulated through a signal transduction pathway involving a Ca 2+ -mediated protein kinase-protein phosphatase system.