In developing xylem, gene expression levels vary in different genotypes, at different stages of development, throughout a growing season, and in response to stresses. Commercially important characteristics such as wood-specific gravity are known to differ with seed source. For example, when grown on a common site, the specific gravity of Arkansas loblolly pine (Pinus taeda L.) trees is greater than that of Louisiana loblolly pine, and Texas loblolly pines have a greater specific gravity than loblolly pines from the Atlantic coast. A microarray analysis was performed to examine variation in gene expression among trees from different geographical sources when grown on a common site, and seasonal variation in gene expression in each seed source. We used microarrays containing 2171 expressed sequence tags (ESTs) with putative functions of interest, selected from several loblolly pine xylem partial cDNA libraries and a shoot tip library. Genes with significant variation in expression for each factor were identified. Many genes preferentially expressed in latewood compared with earlywood were for proteins involved in cell wall biosynthesis. Variation in gene expression among trees from the two seed sources in each growing season suggests that there may be more differences between South Arkansas trees and South Louisiana trees in latewood than in earlywood. Variation in gene expression among trees from different regions may reflect adaptation to different environments.

The main nutritional limitation of maize used for feed is the content of protein that is digestible, bioavailable and contains an amino acid balance that matches the requirements of animals. In contrast, milk protein has good digestibility, bioavailability and amino acid balance. As an initial effort to create maize optimized as a source of swine nutrition, a codon-adjusted version of a gene encoding the milk protein porcine alpha-lactalbumin was synthesized. Maize expression vectors containing this gene under the control of the Ubi-1 promoter and nos 3' terminator were constructed. These vectors were used to transform maize callus lines that were regenerated into fertile plants. The alpha-lactalbumin transgenes were transmitted through meiosis to the sexual progeny of the regenerated plants. Porcine alpha-lactalbumin was detected in callus and kernels from transgenic maize lines that were transformed by two constructs containing the 27-kDa maize gamma-zein signal sequence at the 5' end of the synthetic porcine alpha-lactalbumin coding sequence. One of these constructs contained an ER retention signal and the other did not. Expression was not observed in kernels or callus from transgenic maize lines that were transformed by a construct that does not contain an exogenous protein-targeting signal. This suggests that the signal peptide might play an important role in porcine alpha-lactalbumin accumulation in transgenic maize kernels.

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Arabinogalactan-proteins (AGPs) are a class of large hydroxyproline-rich glycoproteins (HGRPs) found in almost all plant species, and have been implicated in various plant growth and developmental processes including xylogenesis. A total of six AGP-like genes or gene families have been cloned from differentiating pine xylem. In this study, seven different members of the ptaAGP5 gene family with between 54% and 73% similarity at the amino acid level were newly identified. Gene-specific primers were designed and relative transcript levels of 11 loblolly pine AGP and AGP-like genes were examined using real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis. Expression was examined in different tissues: earlywood and latewood; xylem from two populations; drought-stressed and wellwatered roots; compression, opposite and vertical wood; and in vitro cultured cells induced for lignification. The different loblolly pine AGP and AGP-like genes showed varying expression patterns under the different conditions, suggesting different functions for each loblolly pine AGP. The results from this study also suggest that some AGPs are associated with xylogenesis, but not with lignification, and that different xylem AGPs probably have different functions.

In order to meet the protein nutrition needs of the world population, greater reliance on plant protein sources will become necessary. The amino acid balance of most plant protein sources does not match the nutritional requirements of monogastric animals, limiting their nutritional value. In cereals, the essential amino acid lysine is deficient. Maize is a major component of human and animal diets worldwide and especially where sources of plant protein are in critical need such as sub-Saharan Africa. To improve the amino acid balance of maize, we developed transgenic maize lines that produce the milk protein α-lactalbumin in the endosperm. Lines in which the transgene was inherited as a single dominant genetic locus were identified. Sibling kernels with or without the transgene were compared to determine the effect of the transgene on kernel traits in lines selected for their high content of α-lactalbumin. Total protein content in endosperm from transgene positive kernels was not significantly different from total protein content in endosperm from transgene negative kernels in three out of four comparisons, whereas the lysine content of the lines examined was 29-47% greater in endosperm from transgene positive kernels. The content of some other amino acids was changed to a lesser extent. Taken together, these changes resulted in the transgenic endosperms having an improved amino acid balance relative to non-transgenic endosperms produced on the same ear. Kernel appearance, weight, density and zein content did not exhibit substantial differences in kernels expressing the transgene when compared to non-expressing siblings. Assessment of the antigenicity and impacts on animal health will be required in order to determine the overall value of this technology. Abstract In order to meet the protein nutrition needs of the world population, greater reliance on plant protein sources will become necessary. The amino acid balance of most plant protein sources does not match the nutritional requirements of monogastric animals, limiting their nutritional value. In cereals, the essential amino acid lysine is deficient. Maize is a major component of human and animal diets worldwide and especially where sources of plant protein are in critical need such as sub-Saharan Africa. To improve the amino acid balance of maize, we developed transgenic maize lines that produce the milk protein a-lactalbumin in the endosperm. Lines in which the transgene was inherited as a single dominant genetic locus were identified. Sibling kernels with or without the transgene were compared to determine the effect of the transgene on kernel traits in lines selected for their high content of a-lactalbumin. Total protein content in endosperm from transgene positive kernels was not significantly different from total protein content in endosperm from transgene negative kernels in three out of four comparisons, whereas the lysine content of the lines examined was 29-47% greater in endosperm from transgene positive kernels. The content of some other...