Allergenicity assessment of the papaya ringspot virus coat protein expressed in transgenic rainbow papaya

The virus-resistant, transgenic commercial papaya Rainbow and SunUp (Carica papaya L.) have been consumed locally in Hawaii and elsewhere in the mainland United States and Canada since their release to planters in Hawaii in 1998. These papaya are derived from transgenic papaya line 55-1 and carry the coat protein (CP) gene of papaya ringspot virus (PRSV). The PRSV CP was evaluated for potential allergenicity, an important component in assessing the safety of food derived from transgenic plants. The transgene PRSV CP sequence of Rainbow papaya did not exhibit greater than 35% amino acid sequence homology to known allergens, nor did it have a stretch of eight amino acids found in known allergens which are known common bioinformatic methods used for assessing similarity to allergen proteins. PRSV CP was also tested for stability in simulated gastric fluid and simulated intestinal fluid and under various heat treatments. The results showed that PRSV CP was degraded under conditions for which allergenic proteins relative to nonallergens are purported to be stable. The potential human intake of transgene-derived PRSV CP was assessed by measuring CP levels in Rainbow and SunUp along with estimating the fruit consumption rates and was compared to potential intake estimates of PRSV CP from naturally infected nontransgenic papaya. Following accepted allergenicity assessment criteria, our results show that the transgene-derived PRSV CP does not pose a risk of food allergy.     

A review of phosphorus homeostasis and the impact of different types and amounts of dietary phosphate on metabolism and renal health in cats

Elevated concentrations of serum phosphate are linked with progression and increased case fatality rate in animals and humans with chronic kidney disease. Elevated concentrations of serum phosphate can be a risk factor for development of renal and cardiovascular diseases or osteoporosis in previously healthy people. In rodents, an excess intake of dietary phosphorus combined with an inverse dietary calcium : phosphorus ratio (<1 : 1) contributes to renal calcification. Renal injury also has occured in cats fed experimental diets supplemented with highly soluble phosphate salts, especially in diets with inverse calcium : phosphorus ratios. However, not all phosphorus sources contribute similarly to this effect. This review, which focuses on cats, summarizes the published evidence regarding phosphorus metabolism and homeostasis, including the relative impact of different dietary phosphorus sources, and their impact on the kidneys. No data currently shows that commercial cat foods induce renal injury. However, some diets contain high amounts of phosphorus relative to recommendations and some have inverse Ca : P ratios and so could increase the risk for development of kidney disease. While limiting the use of highly soluble phosphates appears to be important, there are insufficient data to support a specific upper limit for phosphate intake. This review also proposes areas where additional research is needed in order to strengthen conclusions and recommendations regarding dietary phosphorus for cats.     

PHOTOSYNTHETIC ACCLIMATION AND DECREASED CHLOROPHYLL(A + B) CONCENTRATIONS OCCUR IN NITROGEN-SUFFICIENT TOBACCO LEAVES IN RESPONSE TO CARBON DIOXIDE ENRICHMENT

Effects of carbon dioxide (CO₂) enrichment on plant growth and on nitrogen partitioning were examined in tobacco (Nicotiana tabacum L. cv. ‘Samsun’). Dry matter, leaf area and specific leaf weight were unchanged (P > 0.05) by CO₂ enrichment. Total soluble protein, soluble amino acids and inorganic nitrate also were unaffected by CO₂ enrichment (P > 0.05). Leaf chlorophyll (a + b) levels decreased 13% (P ≤ 0.05) in response to CO₂ enrichment. The diurnal accumulation of soluble amino acids was delayed and the initial slope of the A/C _i response curve was decreased 14% in the elevated compared to the ambient CO₂ treatment. The above findings showed that CO₂ enrichment affected leaf chlorophyll levels, diurnal soluble amino acid metabolism and photosynthetic responses to low intercellular CO₂ concentrations even though the plants were nitrogen sufficient. Inadequate nitrogen fertility cannot explain all of the effects of CO₂ enrichment on photosynthesis by tobacco leaves.