Journal Articles
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Item Ileal Digestibility of Nitrogen and Amino Acids in Human Milk and an Infant Formula as Determined in Neonatal Minipiglets(Elsevier Inc. on behalf of American Society for Nutrition, 2023-04) Charton E; Henry G; Cahu A; Le Gouar Y; Dahirel P; Moughan PJ; Montoya CA; Bellanger A; Dupont D; Le Huërou-Luron I; Deglaire ABACKGROUND: Infant formula (IF) has to provide at least the same amount of amino acids (AAs) as human milk (HM). AA digestibility in HM and IF was not studied extensively, with no data available for tryptophan digestibility. OBJECTIVES: The present study aimed to measure the true ileal digestibility (TID) of total nitrogen and AAs in HM and IF to estimate AA bioavailability using Yucatan mini-piglets as an infant model. METHODS: Twenty-four 19-day-old piglets (males and females) received either HM or IF for 6 days or a protein-free diet for 3 days, with cobalt-EDTA as an indigestible marker. Diets were fed hourly over 6 h before euthanasia and digesta collection. Total N, AA, and marker contents in diets and digesta were measured to determine the TID. Unidimensional statistical analyses were conducted. RESULTS: Dietary N content was not different between HM and IF, while true protein was lower in HM (-4 g/L) due to a 7-fold higher non-protein N content in HM. The TID of total N was lower (P < 0.001) for HM (91.3 ± 1.24%) than for IF (98.0 ± 0.810%), while the TID of amino acid nitrogen (AAN) was not different (average of 97.4 ± 0.655%, P = 0.272). HM and IF had similar (P > 0.05) TID for most of the AAs including tryptophan (96.7 ± 0.950%, P = 0.079), except for some AAs (lysine, phenylalanine, threonine, valine, alanine, proline, and serine), with small significant difference (P < 0.05). The first limiting AA was the aromatic AAs, and the digestible indispensable AA score (DIAAS) was higher for HM (DIAASHM = 101) than for IF (DIAASIF = 83). CONCLUSION: HM, compared to IF, had a lower TID for total N only, whereas the TID of AAN and most AAs, including Trp, was high and similar. A larger proportion of non-protein N is transferred to the microbiota with HM, which is of physiological relevance, although this fraction is poorly considered for IF manufacturing.Item Review and update of a Nutrient Transfer model used for estimating nitrous oxide emissions from complex grazed landscapes, and implications for nationwide accounting(John Wiley and Sons Inc on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 2022-09-30) Vibart R; Giltrap D; Saggar S; Mackay A; Betteridge K; Costall D; Rollo M; Draganova I; Zhu-Barker. XIn New Zealand, nitrous oxide emissions from grazed hill pastures are estimated using different emission factors for urine and dung deposited on different slope classes. Allocation of urine and dung to each slope class needs to consider the distribution of slope classes within a landscape and animal behavior. The Nutrient Transfer (NT) model has recently been incorporated into the New Zealand Agricultural GHG Inventory Model to account for the allocation of excretal nitrogen (N) to each slope class. In this study, the predictive ability of the transfer function within the NT model was explored using urine deposition datasets collected with urine sensor and GPS tracker technology. Data were collected from three paddocks that had areas in low (<12°), medium (12-24°), and high slopes (>24°). The NT model showed a good overall predictive ability for two of the three datasets. However, if the urine emission factors (% of urine N emitted as N2 O-N) were to be further disaggregated to assess emissions from all three slope classes or slope gradients, more precise data would be required to accurately represent the range of landscapes found on farms. We have identified the need for more geospatial data on urine deposition and animal location for farms that are topographically out of the range used to develop the model. These new datasets would provide livestock urine deposition on a more continuous basis across slopes (as opposed to broad ranges), a unique opportunity to improve the performance of the NT model.Item Transcriptomic Identification of a Unique Set of Nodule-Specific Cysteine-Rich Peptides Expressed in the Nitrogen-Fixing Root Nodule of Astragalus sinicus(The American Phytopathological Society in cooperation with the International Society for Molecular Plant-Microbe Interactions, 2022-10-08) Wei F; Liu Y; Zhou D; Zhao W; Chen Z; Chen D; Li Y; Zhang X-XLegumes in the inverted repeat-lacking clade (IRLC) each produce a unique set of nodule-specific cysteine-rich (NCR) peptides, which act in concert to determine the terminal differentiation of nitrogen-fixing bacteroid. IRLC legumes differ greatly in their numbers of NCR and sequence diversity. This raises the significant question how bacteroid differentiation is collectively controlled by the specific NCR repertoire of an IRLC legume. Astragalus sinicus is an IRLC legume that forms indeterminate nodules with its microsymbiont Mesorhizobium huakuii 7653R. Here, we performed transcriptome analysis of root and nodule samples at 3, 7, 14, 28 days postinoculation with M. huakuii 7653R and its isogenic ∆bacA mutant. BacA is a broad-specificity peptide transporter required for the host-derived NCRs to target rhizobial cells. A total of 167 NCRs were identified in the RNA transcripts. Comparative sequence and electrochemical analysis revealed that A. sinicus NCRs (AsNCRs) are dominated by a unique cationic group (termed subgroup C), whose mature portion is relatively long (>60 amino acids) and phylogenetically distinct and possessing six highly conserved cysteine residues. Subsequent functional characterization showed that a 7653R variant harboring AsNCR083 (a representative of subgroup C AsNCR) displayed significant growth inhibition in laboratory media and formed ineffective white nodules on A. sinicus with irregular symbiosomes. Finally, bacterial two-hybrid analysis led to the identification of GroEL1 and GroEL3 as the molecular targets of AsNCR067 and AsNCR076. Together, our data contribute to a systematic understanding of the NCR repertoire associated with the A. sinicus and M. huakuii symbiosis.Item Role of a local transcription factor in governing cellular carbon/nitrogen homeostasis in Pseudomonas fluorescens(Oxford University Press on behalf of Nucleic Acids Research, 2021-04-06) Naren N; Zhang X-XAutoactivation of two-component systems (TCSs) can increase the sensitivity to signals but inherently cause a delayed response. Here, we describe a unique negative feedback mechanism enabling the global NtrB/NtrC regulator to rapidly respond to nitrogen starvation over the course of histidine utilization (hut) in Pseudomonas fluorescens. NtrBC directly activates transcription of hut genes, but overexpression will produce excess ammonium leading to NtrBC inactivation. To prevent this from occurring, the histidine-responsive repressor HutC fine-tunes ntrBC autoactivation: HutC and NtrC bind to the same operator site in the ntrBC promoter. This newly discovered low-affinity binding site shows little sequence similarity with the consensus sequence that HutC recognizes for substrate-specific induction of hut operons. A combination of genetic and transcriptomic analysis indicated that both ntrBC and hut promoter activities cannot be stably maintained in the ΔhutC background when histidine fluctuates at high concentrations. Moreover, the global carbon regulator CbrA/CbrB is involved in directly activating hut transcription while de-repressing hut translation via the CbrAB-CrcYZ-Crc/Hfq regulatory cascade. Together, our data reveal that the local transcription factor HutC plays a crucial role in governing NtrBC to maintain carbon/nitrogen homeostasis through the complex interactions between two TCSs (NtrBC and CbrAB) at the hut promoter.Item Nutrient criteria to achieve New Zealand's riverine macroinvertebrate targets(PeerJ, Inc, 2021) Canning AD; Joy MK; Death RG; Brauns MWaterways worldwide are experiencing nutrient enrichment from population growth and intensive agriculture, and New Zealand is part of this global trend. Increasing fertilizer in New Zealand and intensive agriculture have driven substantial water quality declines over recent decades. A recent national directive has set environmental managers a range of riverine ecological targets, including three macroinvertebrate indicators, and requires nutrient criteria be set to support their achievement. To support these national aspirations, we use the minimization-of-mismatch analysis to derive potential nutrient criteria. Given that nutrient and macroinvertebrate monitoring often does not occur at the same sites, we compared nutrient criteria derived at sites where macroinvertebrates and nutrients are monitored concurrently with nutrient criteria derived at all macroinvertebrate monitoring sites and using modelled nutrients. To support all three macroinvertebrate targets, we suggest that suitable nutrient criteria would set median dissolved inorganic nitrogen concentrations at ~0.6 mg/L and median dissolved reactive phosphorus concentrations at ~0.02 mg/L. We recognize that deriving site-specific nutrient criteria requires the balancing of multiple values and consideration of multiple targets, and anticipate that criteria derived here will help and support these environmental goals.Item Hagfish feeding habits along a depth gradient inferred from stable isotopes(27/06/2013) Zintzen V; Rogers KM; Roberts CD; Stewart AL; Anderson MJFeeding habits of 3 hagfish species were investigated along a depth gradient (~50 to 900 m) in New Zealand using nitrogen (?15N) and carbon (?13C) stable isotopes. Neomyxine biniplicata had the lowest mean ?15N value (14.2%), followed by Eptatretus cirrhatus (14.9 %) and Eptatretus sp. 1 (15.8%). Neomyxine biniplicata (~50 m depth) was characterized by (1) relative low lipid content in muscles and (2) consistent body condition index which together with its trophic position indicated that this species probably acquires its food by active predation, supplemented by opportunistic scavenging. Eptatretus cirrhatus (48 to 912 m) and Eptatretus sp. 1 (290 to 922 m) had similar morphology, but their ?15N signature indicated that they were feeding on slightly different trophic levels. For Eptatretus sp. 1, the combination of (1) variable lipid content, indicating phases of feeding and fasting, (2) decreasing body condition index with depth, indicating less regular feeding at depth, (3) increasing ?15N with depth and (4) decreasing ?13C signature with depth, pointed towards a feeding behaviour specialized in scavenging on large but rare falls of high-level predators such as whales, sharks or bony fishes. On the other hand, E. cirrhatus was characterized by (1) less variable lipid content, (2) a body condition index not influenced by depth, (3) ?15N values decreasing with depth and ?13C values constant across its depth range, which is likely to indicate a more opportunistic and mobile feeding behaviour on a range of prey © 2013 Museum of New Zealand Te Papa Tongarewa and Massey University and GNS Science.