To address the problem of manure-based environmental pollution in the pork industry, we have developed the phytase transgenic pig. The saliva of these pigs contains the enzyme phytase, which allows the pigs to digest the phosphorus in phytate, the most abundant source of phosphorus in the pig diet. Without this enzyme, phytate phosphorus passes undigested into manure to become the single most important manure pollutant of pork production. We show here that salivary phytase provides essentially complete digestion of dietary phytate phosphorus, relieves the requirement for inorganic phosphate supplements, and reduces fecal phosphorus output by up to 75%. These pigs offer a unique biological approach to the management of phosphorus nutrition and environmental pollution in the pork industry.

Pea seed-borne mosaic potyvirus (PSbMV) isolates are divided into pathotypes P-1, P-2, and P-4 according to their infection profile on a panel of Pisum sativum lines. P. sativum PI 269818 is resistant to P-1 and P-2 isolates and is susceptible to P-4 isolates. Resistance to P-1 is inherited as a single recessive gene, denoted sbm-1, and the pathogenicity determinant has previously been mapped to the virus-coded protein VPg. In the cultivar Bonneville, a second recessive gene, sbm-2, confers specific resistance to P-2. By exchanging cistrons between a P-2 and a P-4 isolate, the P3-6k1 cistron was identified as the PSbMV host-specific pathogenicity determinant on Bonneville. Exchange of P3-6k1 did not affect infection on PI 269818, and infection of Bonneville was not altered by substitution of the VPg cistron, indicating that P3-6k1 and VPg are independent determinants of pathotype-specific infectivity. On PI 269818 the pathogenicity determinant of both P-1 and P-2 mapped to the N terminus of VPg. This suggests that VPg from the P-1 and P-2 isolates are functionally similar on this host and that resistance to P-1 and P-2 in PI 269818 may operate by the same mechanism. Identification of VPg-sbm-1 and P3-6k1-sbm-2 as independent pairs of genetic interactors between PSbMV and P. sativum provides a simple explanation of the three known pathotypes of PSbMV. Furthermore, analysis of ␤-glucuronidase-tagged P-2 virus indicated that sbm-2 resistance affected an early step in infection, implying that the P3-6k1 region plays a critical role in potyvirus replication or cell-to-cell movement.

The murine parotid secretory protein (PSP) gene is expressed selectively at high levels in parotid and sublingual salivary glands. Previously, the transcriptional activity of a PSP mini-gene, called Lama, was shown to be dependent on a 1.5 kb region located 3 kb upstream of the transcription start site. Here, functional studies in transgenic mice demonstrate that this proximal regulatory region has properties of a parotid and sublingual gland specific enhancer. Protein-binding experiments identify multiple sequence-specific binding complexes spanning the entire 1.5 kb enhancer region. Several sequence elements bound specifically by parotid and/or sublingual gland nuclear extracts, including consensus binding elements for previously described transcription factors as well as novel binding elements are located in the proximal enhancer region. A deletion analysis of the enhancer region in transgenic mice identified a core sequence of 700 bp. This region contains five elements bound specifically by nuclear proteins isolated from the PSP-expressing parotid and sublingual glands. Two of these elements, denoted parotid gland element I (PGE I) and sublingual gland element I (SLE I), are novel salivary gland specific binding elements, bound uniquely by parotid and sublingual gland nuclear extracts, respectively.

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