Consequences to fertilization of the developmental stage of apricot ovules at anthesis

Summary

Flowers at anthesis from the apricot cvs Palstein and Goldrich were examined to determine their ovule maturity stage. Further, flowers from both cultivars were pollinated and collected after 2000 and 3000 growing degree hours (GDH) in two consecutive years. Numbers of fertilized ovules were recorded in those flowers. Ovules of ‘Palstein’ from flowers at anthesis showed predominantly an embryo sac at the eight nuclei stage of development while embryo sacs in ‘Goldrich’ were mainly in a four nuclei stage. After 2000 GDH from pollination 90% of viable ovules were fertilized in ‘Palstein’ whereas only 37.5% of them were fertilized in ‘Goldrich’. After 3000 GDH, Goldrich presented the same percentage of fertilized ovules that was recorded after 2000 GDH. Non-fertilized ovules did not degenerate and developed normally in pollinated and non-pollinated flowers from both cultivars. Further, non-fertilized pollinated flowers were not different from non-pollinated flowers in the development of the embryo sac, indicating that the chances for fertilization would not be increased by pollination in apricot. We suggest that the lack of fertilization in ‘Goldrich’ is due to degeneration of the male gametophyte, which would have a limited life, not long enough for the embryo sacs to develop to maturity.     

苎麻生物脱胶复合菌群的构建

分别从沤麻池、苎麻脱胶厂污泥、老麻园土和腐烂麻堆等生境收集自然菌群,采用室内温水沤麻的方法检测它们的原始脱胶能力,结果表明:这些自然菌群的脱胶能力较弱,使苎麻分纤分别需要12 d、18 d、14 d和10 d,脱胶后的纤维强度极低,最高只有2.83 cN/dtex,失去了工业利用价值.将不同来源的菌群等比例混后用于脱胶试验,其分纤周期为8d,分纤时纤维强为2.58 cN/dtex.以苎麻为唯一碳源和能源对复合菌群进行长期驯化,分别在驯化至69 d、89 d、182 d和407 d发现其分纤周期缩短到了5d、4d、3d和2.2 d,而且随着分纤周期的缩短,纤维强度也逐渐提高.复合菌群驯化407d后,分纤周期稳定在50h左右,分纤状况良好,纤维强度达到了5.52 cN/dtex.     

Pink‐awned weedy rice (Oryza sativa): a potential conduit for gene exchange in rice agro‐ecosystems

Hybridisation between genetically distinct lineages results in increases in overall genetic diversity and is a potential mechanism for the origin and spread of adaptive alleles. Weed and crop hybridisation may result in weedy ecotypes, which have, in addition to classic weedy traits such as seed shattering and long seed dormancy, crop traits that enhance weediness, such as adaptation to field cultivation and harvest strategies. Weedy rice (Oryza sativa) hybridises with cultivated rice and, in the process, may produce new (pink‐awned) weedy rice varieties. Pink‐awned (PA) weedy rice plants have been observed in rice fields in Arkansas. We explored the genetic relationships between PA weedy rice, crop rice, global rice accessions and other weedy rice ecotypes present in the southern United States. Gene sequencing of 48 sequence‐tagged sites (STS loci) revealed a pattern of hybridisation and gene flow between blackhull weedy rice and tropical japonica rice (O. sativa subsp. japonica) cultivars. Our data suggest that PA rice originates from hybridisation between blackhull weedy rice and tropical japonica rice. PA rice offspring segregate phenotypic traits associated with weediness in rice. This segregation could lead to adaptive allele combinations in PA rice, which could potentially move into other weedy rice types through subsequent hybridisation events.     

IGF-1 stimulates protein synthesis by enhanced signaling through mTORC1 in bovine mammary epithelial cells

Using the MAC-T cell line as a model, the effects of insulin-like growth factor (IGF)-1 on the regulation of protein synthesis through the mammalian target of rapamycin complex 1 (mTORC1) signaling in bovine mammary epithelial cells were evaluated. Global rates of protein synthesis increased by 47% within 30 min of IGF-1 treatment. The effect of IGF-1 on protein synthesis was associated with enhanced association of the eukaryotic initiation factor (eIF) 4E with eIF4G and a concomitant reduction of eIF4E association with eIF4E-binding protein-1 (4E-BP1). There was a progressive increase in the phosphorylation state of ribosomal protein S6 kinase-1, a downstream target of mTORC1 in response to IGF-1. In addition, IGF-1 stimulated mTORC1 kinase activity toward 4E-BP1 in vitro. Phosphorylation on Ser473 of Akt was induced by IGF-1 within 5 min and remained elevated throughout a 30-min time course. The effect of IGF-1 on Akt phosphorylation was also concentration dependent. Activation of Akt by IGF-1 led to increased phosphorylation of tuberous sclerosis complex 2 on Thr1426, without any change in its association with tuberous sclerosis complex 1. Phosphorylation of proline-rich Akt substrate of 40-kDa (PRAS40) at Thr246 was stimulated by IGF-1. The amount of PRAS40 associated with mTORC1 decreased in response to IGF-1, and PRAS40 binding to mTORC1 was inversely related to its phosphorylation level. Overall, these results suggest that activation of the PI3K-Akt pathway by IGF-1 stimulated global protein synthesis in bovine mammary epithelial cells through changes in the phosphorylation and association state of components of the mTORC1 signaling pathway.     

营养素和催乳激素通过哺乳动物雷帕霉素靶点调控乳蛋白的合成

研究结果表明,营养和内分泌系统影响奶牛乳腺内乳蛋白的翻译过程,但其分子机制还不是很清楚。因此,本试验旨在研究营养素和激素通过哺乳动物雷帕霉素(mTOR)信号路径对乳蛋白合成的影响。氨基酸混合物(AA)、能量底物(葡萄糖和醋酸盐)和激素混合物(皮质醇、胰岛素和催乳素)分别或混合添加到培养乳腺腺泡(泌乳奶牛乳腺中分离)的培养媒介中,同时测定乳蛋白合成和mTOR信号路径元件的磷酸化状态。结果表明,AA单独添加时比能量底物或激素混合物单独添加时,乳蛋白的合成提高50%。乳蛋白的合成不受葡萄糖或催乳素的影响。AA能刺激乳蛋白的合成,催乳素同时添加能够进一步增强乳蛋白的合成,但葡萄糖同时添加不能增强这种作用。催乳素能够诱导蛋白激酶B的磷酸化状态,并且AA或葡萄糖同时作为底物时能够增强这种磷酸化状态。AA和催乳素在刺激乳蛋白的合成和进一步提高乳蛋白合成的同时,也提高了mTOR底物(p70核糖体蛋白S6激酶±1、真核起始因子4E(eIF4E)结合蛋白-1(4E-BP1)和4E-BP1的分化异变体)的磷酸化状态。结果暗示营养素和激素可能通过mTOR信号路径调控乳蛋白的合成。     

Resistance levels and fitness of protoporphyrinogen oxidase (PROTOX) inhibitor-resistant transgenic rice in paddy fields

We previously confirmed that the transgenic rice line, M4, was about 200-fold more resistant to oxyfluorfen than the wild-type (WT) rice in whole-plant bioassays in pots. The transgenic rice line was also cross-resistant to other protoporphyrinogen oxidase (PROTOX)-inhibiting herbicides, acifluorfen, carfentrazone, and oxadiazon. The objectives of this research were to (a) verify the resistance of transgenic rice plants to commercial doses of PROTOX-inhibiting herbicides under paddy field conditions, (b) compare the growth, yield, and grain quality of transgenic and WT rice under weed-free conditions in a paddy field, and (c) determine the responses of transgenic and WT rice plants to chilling and drought stress. In the field, M4 was resistant to PROTOX inhibitors oxyfluorfen, acifluorfen, carfentrazone, pyraflufen, and oxadiazon in transplanted and direct-seeded rice culture. The transgenic and WT plants had similar plant heights and number of tillers. However, the yield of M4 at T₄ and T₅ generations was 7–8% less than that of WT plants. This was due to reduced number of spikelets per panicle and reduced grain weight. Head rice yield, immature kernels, damaged kernels, palatability, and protein and amylose contents were similar between M4 and WT rice. There was no difference in chilling injury between WT and M4, but M4 was more tolerant to drought stress than WT plants. PROTOX inhibitor-resistant rice is agronomically viable. It will expand the herbicide options in rice production. Follow-up research is required to elucidate the mechanisms underlying the slight yield difference and differential drought response between WT and transgenic rice.     

Failure of zinc supplementation to prevent severe facial eczema in cattle fed excess copper

CASE HISTORY: A 400-cow dairy unit in the Waikato suffered a severe outbreak of facial eczema (FE) despite consistent zinc supplementation and significantly elevated serum zinc concentrations.

CLINICAL FINDINGS: FE prevention had begun in mid-January 2006, via zinc sulphate supplementation in the water. Photosensitisation was reported on 06 April, contemporaneous with a marked increase in the number of Pithomyces chartarum spores in pasture samples. Within 10 days of this first clinical case, 100 affected cows had been dried off, eight of which subsequently died or were culled. Blood samples were collected from ten affected cows; all had serum zinc concentrations >17 µmol/L, and eight had gamma-glutamyl transferase (GGT) activities >200 U/ml, indicating that the photosensitisation was secondary to liver damage, i.e. probably FE. Further investigation identified that this herd had been receiving excess copper supplementation; 4/6 culled cows had liver copper concentrations within or above the marginal range for copper toxicity.

DIAGNOSIS: Severe FE despite zinc supplementation that increased serum zinc concentrations above recommended levels

CLINICAL RELEVANCE: As zinc supplementation significantly reduces apparent copper status, copper supplementation is often used to counteract this. Previous excess copper intake may reduce the efficacy of zinc in preventing FE, thus copper intake should be assessed prior to the start of zinc supplementation.     

Agronomic and Physiological Study of Cold and Flooding Tolerance of Spelt (Triticum spelta L.) and Wheat (Triticum aestivum L.)

Flooding of soil occurs all over the world in areas of crop production. The resulting lack of available oxygen in the soil can hinder the establishment of field crops such as wheat ( Triticum aestivum L.) and thus lead to a decrease in yield. The current study compares the tolerance of spelt ( Triticum spelta L.) and wheat to wet and cold stress during germination and early growth. Two specific traits seem to be related to the superior early flooding tolerance of spelt: (1) fast growth of the coleoptile, which reaches the soil surface rapidly, thus reducing the time span of hypoxia sensitivity, independent of temperatures between 10 and 20 °C; (2) the improved physiological adaptation for coleoptile growth under hypoxia is probably due to lower oxygen consumption between germination and emergence. Because of this high level of flooding tolerance, spelt would also be a good source for breeding for stress tolerance in wheat. These findings will help to detect quantitative trait loci (QTL) for characters such as growth rate, flooding tolerance and oxygen consumption in future studies. A marker-assisted introgression of spelt into wheat is necessary to avoid combination with undesirable agronomic traits of spelt.