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Chitinases, beta-1,3-glucanases, and ribosome-inactivating proteins are reported to have antifungal activity in plants. With the aim of producing fungus-resistant transgenic plants, we co-expressed a modified maize ribosome-inactivating protein gene, MOD1, and a rice basic chitinase gene, RCH10, in transgenic rice plants. A construct containing MOD1 and RCH10 under the control of the rice rbcS and Act1 promoters, respectively, was co-transformed with a plasmid containing the herbicide-resistance gene bar as a selection marker into rice by particle bombardment. Several transformants analyzed by genomic Southern-blot hybridization demonstrated integration of multiple copies of the foreign gene into rice chromosomes. Immunoblot experiments showed that MOD1 formed approximately 0.5% of the total soluble protein in transgenic leaves. RCH10 expression was examined using the native polyacrylamide-overlay gel method, and high RCH10 activity was observed in leaf tissues where endogenous RCH10 is not expressed. R1 plants were analyzed in a similar way, and the Southern-blot patterns and levels of transgene expression remained the same as in the parental line. Analysis of the response of R2 plants to three fungal pathogens of rice, Rhizoctonia solani, Bipolaris oryzae, and Magnaporthe grisea, indicated statistically significant symptom reduction only in the case of R. solani (sheath blight). The increased resistance co-segregated with herbicide tolerance, reflecting a correlation between the resistance phenotype and transgene expression.

Plant protein is the primary source of all dietary protein for humans and livestock. In 1992, world protein production was 137 million metric tons, of which 65% was obtained from plants directly and 35% through animal protein production.' In comparison to meat protein, plant protein is more economic to produce and convenient to transport and store. However, when used as a source of dietary protein for human and monogastric animals, most plant proteins are nutritionally incomplete because of their deficiency in certain essential amino acids. In general, cereal proteins are low in lysine (Lys) and tryptophan (Trp), and legume and most vegetable proteins are deficient in the sulfur amino acids methionine (Met) and cysteine (CYS).~ Amino acid deficiencies can be corrected in at least three ways, namely, supplementation with synthetic amino acids, supplementation with small amounts of protein which are a rich source of the deficient amino acid(s), or complementation with other protein(s) so that the combined protein sources will balance each other's deficiencies or excesses. The American animal feed industry annually spends 150 and 70 million dollars on synthetic Met and Lys, respectively, to supplement the protein base feeds. Conventional plant breeding methods have made some progress in identifying mutations with improved seed protein quality, such as high-Lys corn and barley.3 However, the undesirable traits associated with these mutations, such as lower yields and greater susceptibility to pests and diseases, have prevented their agronomic uti l i~ation.~ Because of a lack of genetic variability in Met content, efforts to breed legumes with increased levels of Met have not had significant success. Recent advances in biotechnology offer alternative approaches to improving the nutritional quality of plant proteins. These include sequence modifications, synthetic genes, overexpression of homologous genes, and transfer and expression of heterologous genes. Progress in this area of research and development was reviewed r e ~ e n t l y . ~ , ~

2S seed proteins were purified from paradise nut (Lecythis zabucajo) and cannonball (Couroupita quianensis), two members of the Brazil nut family (Lecythidaceae). The amino acid composition, subuni...

Chitinases, beta-1,3-glucanases, and ribosome-inactivating proteins are reported to have antifungal activity in plants. With the aim of producing fungus-resistant transgenic plants, we co-expressed a modified maize ribosome-inactivating protein gene, MOD1, and a rice basic chitinase gene, RCH10, in transgenic rice plants. A construct containing MOD1 and RCH10 under the control of the rice rbcS and Act1 promoters, respectively, was co-transformed with a plasmid containing the herbicide-resistance gene bar as a selection marker into rice by particle bombardment. Several transformants analyzed by genomic Southern-blot hybridization demonstrated integration of multiple copies of the foreign gene into rice chromosomes. Immunoblot experiments showed that MOD1 formed approximately 0.5% of the total soluble protein in transgenic leaves. RCH10 expression was examined using the native polyacrylamide-overlay gel method, and high RCH10 activity was observed in leaf tissues where endogenous RCH10 is not expressed. R1 plants were analyzed in a similar way, and the Southern-blot patterns and levels of transgene expression remained the same as in the parental line. Analysis of the response of R2 plants to three fungal pathogens of rice, Rhizoctonia solani, Bipolaris oryzae, and Magnaporthe grisea, indicated statistically significant symptom reduction only in the case of R. solani (sheath blight). The increased resistance co-segregated with herbicide tolerance, reflecting a correlation between the resistance phenotype and transgene expression.

Progeny of two transgenic tobacco (Nicotiana tabacum L.) lines that expressed an activated form of maize (Zea mays L.) ribosome-inactivating protein (RIP) had varying resistance to the insect species tested. A subset of R(2) plants from the two lines appeared to be more resistant to larvae of the cigarette beetle, Lasioderma serricorne (F.), and the tobacco hornworm, Manduca sexta (L.) than the wild type plants. Progeny (R(3)) of the more resistant R(2) plants were tested more extensively for insect resistance. Resistance to the corn earworm, Helicoverpa zea (Boddie), was most consistent, with significantly decreased feeding often accompanied by increased mortality and reduced weights of survivors fed on leaf disks of the two transgenic lines compared to the wild type. The amount of damage by H. zea was significantly inversely correlated with levels of RIP. Resistance of RIP-producing plants to H. zea was greater than expected on the basis of prior in vitro results using diet-incorporated maize RIP. The R(3) transgenic plant leaf disks were also often more resistant to feeding by larvae of L. serricorne compared to wild type plants. Although reduced feeding by M. sexta was noted when they were fed leaf disks from transgenic compared to wild type plants the first day of exposure, differences were not significant. This information provides further support for maize RIP having a role in resistance to maize-feeding insects.