Biofuels provide a potential route to avoiding the global political instability and environmental issues that arise from reliance on petroleum. Currently, most biofuel is in the form of ethanol generated from starch or sugar, but this can meet only a limited fraction of global fuel requirements. Conversion of cellulosic biomass, which is both abundant and renewable, is a promising alternative. However, the cellulases and pretreatment processes involved are very expensive. Genetically engineering plants to produce cellulases and hemicellulases, and to reduce the need for pretreatment processes through lignin modification, are promising paths to solving this problem, together with other strategies, such as increasing plant polysaccharide content and overall biomass.

Within the last 10 years, much attention has been focused on the role chitinases play within the plant. Evidence is strong that they are antifungal proteins, yet they may also play a part in a nonspecific stress response and can be developmentally regulated. They consist of several enzyme classes and are produced in many plants by small gene families. This review discusses the nature of these enzymes and the genes that encode them, developmental- and tissue-specific expression, and the classes of organic and inorganic molecules which induce chitinase gene expression and accumulation. Prospects for the development of fungus-resistant varieties of plants using "foreign" chitinase genes are also analyzed. Key words: pathogenesis-related protein, antifungal protein, gene regulation, induction, hydrolase.

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The catalytic domain of Acidothermus cellulolyticus thermostable endoglucanase gene (encoding for endo-1,4-beta-glucanase enzyme or E1) was constitutively expressed in rice. Molecular analyses of T1 plants confirmed presence and expression of the transgene. The amount of E1 enzyme accounted for up to 4.9% of the plant total soluble proteins, and its accumulation had no apparent deleterious effects on plant growth and development. Approximately 22 and 30% of the cellulose of the Ammonia Fiber Explosion (AFEX)-pretreated rice and maize biomass respectively was converted into glucose using rice E1 heterologous enzyme. As rice is the major food crop of the world with minimal use for its straw, our results suggest a successful strategy for producing biologically active hydrolysis enzymes in rice to help generate alcohol fuel, by substituting the wasteful and polluting practice of rice straw burning with an environmentally friendly technology.

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We have developed a nove1 and reproducible system for recovery of fertile transgenic maize (Zea mays L.) plants. The transformation was performed using microprojectile bombardment of cultured shoot apices of maize with a plasmid carrying two linked genes, the Strepfomyces bygroscopicus phosphinothricin acetyltransferase gene (bar) and the potato proteinase inhibitor II gene, either alone or in combination with another plasmid containing the 5' region of the rice actin 1 gene fused to the Escbericbia coli p-glucuronidase gene (gus). Bombarded shoot apices were subsequently multiplied and selected under 3 to 5 mg/L glufosinate ammonium. Co-transformation frequency was 100% (146/146) for linked genes and 80% (41/51) for unlinked genes. Co-expression frequency of the bar and gus genes was 5 7 % (29/51). The co-integration, co-inheritance, and co-expression of bar, the potato proteinase inhibitor II gene, and gus in transgenic R,, R,, and R, plants were confirmed. Localized expression of the actin 1-CUS protein in the R, and R, plants was extensively analyzed by histochemical and fluorometric assays.The shoot tip, or shoot apex, consists of the shoot apical meristem, a region in which lateral organ primordia form, a subapical region of cell enlargement, and severa1 leaf primordia (Steeves and Sussex, 1989). The meristem region contains apical initial cells and subepidermal cells from which the gametes are derived (Medford, 1992). Theoretically, there are two possibilities for recovering transgenic plants via transfer of DNA into the shoot apical meristem. One possibility is that transgenic progeny may be directly produced via transformation of the subepidermal germline cells followed by the development of a partially transgenic reproductive organ. In this case, the primary transformants will always be chimeric. An alternative possibility is to multiply transgenic apical meristem cells and/or germ-line cells, which can be reprogrammed in the developmental direction under in vitro conditions. Transgenic plants can be regenerated from these cells with or without selection. Our previous research on maize (Zea mays L.) morphogenesis demonstrated that the maize meristem is morphogenetically plastic and can be manipulated to produce multiple shoots, somatic embryos, tassels, or ears in a relatively genotype-independent manner by simple variation of in vitro culture conditions (Zhong et al., 1992a(Zhong et al., , 1992b. Based on this concept, we transformed maize meristems via microprojectile bombardment with a series of chimeric genes, including bar, pin2, and gus.In this paper, we report the efficient recovery of fertile transgenic maize plants via a shoot-multiplication system after microprojectile bombardment of shoot tips. Maize shoot apices were transformed with a plasmid incorporating bar driven by the CaMV 35s promoter and pin2 with the wound-inducible pin2 promoter (Fig. l), either alone or in combination with another plasmid containing gus driven by the 5' region of Actl (Fig. 1). The co-integration and co-inherita...

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One of the goals of the U.S. government is to have “cellulosic ethanol” produced from a variety of sources, including feedstock crop biomass (a mass of raw material used in alcohol fuels processing), because these biomass sources contain polysaccharides that can be converted into fermentable sugars. Furthermore, the feedstock biomass sources are renewable and could become available at a billion tonnes per year in the United States. There are three major steps associated with the conversion of feedstock biomass into cellulosic ethanol. The first is the production of hydrolysis enzymes such as microbial cellulases, which convert the cellulose of feedstock biomass into fermentable sugars. The second step is the pretreatment processes used to break down the recalcitrant lignocellulose complex of feedstock into more reactive intermediates and to remove the lignin residues so the cellulase enzymes can have access to cellulose. The third step is fermentation of sugars into ethanol. The first two steps are the subject of this review. Plant genetic engineering has been used to directly express heterologous versions of cellulase and hemicellulase enzymes in situ. Plants have also been genetically modified for less lignin content or for more digestible lignin. An increase in feedstock polysaccharides and an increase in overall crop biomass via crop genetic engineering have also been reported. This article reviews the advancements made in feedstock crop genetic engineering in the above areas and discusses possible near‐future perspectives.