Mitogen-activated protein kinase (MAPK) cascades play pivotal roles in plant responses to both biotic and abiotic stress. A screen of a Nicotiana benthamiana cDNA virus-induced gene silencing (VIGS) library for altered plant responses to inoculation with Phytophthora infestans previously identified an NbMKK gene, encoding a clade D MAPKK that we renamed as NbMKK5, which is involved in immunity to P. infestans. To study the role of the potato orthologous gene, referred to as StMKK5, in the response to P. infestans, we transiently overexpressed StMKK5 in N. benthamiana and observed that cell death occurred at 2 days postinfiltration. Silencing of the highly conserved eukaryotic protein SGT1 delayed the StMKK5-induced cell death, whereas silencing of the MAPK-encoding gene NbSIPK completely abolished the cell death response. Further investigations showed that StMKK5 interacts with, and directly phosphorylates, StSIPK. Furthermore, both StMKK5 and StSIPK trigger salicylic acid (SA)- and ethylene (Eth)-related gene expression, and co-expression of the salicylate hydroxylase NahG with the negative regulator of Eth signalling CTR1 hampers StSIPK-triggered cell death. This observation indicates that the cell death triggered by StMKK5-StSIPK is dependent on the combination of SA- and Eth-signalling. By introducing point mutations, we showed that the kinase activity of both StMKK5 and StSIPK is required for triggering cell death. Genetic analysis showed that StMKK5 depends on StSIPK to trigger plant resistance. Thus, our results define a potato StMKK5-SIPK module that positively regulates immunity to P. infestans via activation of both the SA and Eth signalling pathways. 相似文献
Flowering time is one of important agronomic traits determining the crop yield and affected by high temperature. When facing high ambient temperature, plants often initiate early flowering as an adaptive strategy to escape the stress and ensure successful reproduction. However, here we find opposing ways in the short-day crop soybean to respond to different levels of high temperatures, in which flowering accelerates when temperature changes from 25 to 30 °C, but delays when temperature reaches 35 °C under short day. phyA-E1, possibly photoperiodic pathway, is crucial for 35 °C-mediated late flowering, however, does not contribute to promoting flowering at 30 °C. 30 °C-induced up-regulation of FT2a and FT5a leads to early flowering, independent of E1. Therefore, distinct responsive mechanisms are adopted by soybean when facing different levels of high temperatures for successful flowering and reproduction. 相似文献
This paper reports a sequence of a Ca3YAl3B4O15:xEu3+ red phosphor prepared using a high-temperature solid-state reaction. At the excitation of 396 nm, the samples emitted intense red emission centred at ~623 nm, which could be attributed to the 5D0→7F2 transition of the Eu3+ ion. The results showed that the optimum Eu3+ doping concentration of Ca3YAl3B4O15:Eu3+ phosphor was x = 80 mol%, and the concentration quenching mechanism of Ca3YAl3B4O15:Eu3+ red phosphor belonged to the exchange coupling between Eu3+ ions. The Commission Internationale de l'éclairage (CIE) coordinates and colour purity of Ca3Y0.2Al3B4O15:0.8Eu3+ were calculated as (0.6375, 0.3476) and 95.5%, respectively. Moreover, the red emission of the obtained phosphor Ca3YAl3B4O15:0.8Eu3+ exhibited a low thermal quenching behaviour with an intensity retention rate of 92.85% at 150°C. The above results manifest that the Eu3+-activated Ca3YAl3B4O15 phosphor is predicted to be a promising red luminescent component for white light-emitting diodes. 相似文献
The lactose-protease plasmid pUCL22 of Lactococcus lactis subsp. lactis strain CNRZ270 contained two inverted copies of IS 1076 flanking a region of 3.7 kb. This internal region was sequenced and found to contain two large open reading frames, ORF1 and ORFP in opposite orientations. ORF1 consists of 2289 bp; the deduced 763-amino-acid sequence is similar to the ATPases of the ClpA family. It contains two well-conserved consensus ATP-binding sites. It was named ClpL. ORFP consists of 930 bp encoding a protein of 310 amino acids. No similarity with any known protein was found in GenBank data for ORFP. Increased ATP-dependent proteolytic activity was detected in extracts from Escherichia coli cells expressing the clpL and ORFP genes. 相似文献
In observational cohort studies with complex sampling schemes, truncation arises when the time to event of interest is observed only when it falls below or exceeds another random time, that is, the truncation time. In more complex settings, observation may require a particular ordering of event times; we refer to this as sequential truncation. Estimators of the event time distribution have been developed for simple left-truncated or right-truncated data. However, these estimators may be inconsistent under sequential truncation. We propose nonparametric and semiparametric maximum likelihood estimators for the distribution of the event time of interest in the presence of sequential truncation, under two truncation models. We show the equivalence of an inverse probability weighted estimator and a product limit estimator under one of these models. We study the large sample properties of the proposed estimators and derive their asymptotic variance estimators. We evaluate the proposed methods through simulation studies and apply the methods to an Alzheimer's disease study. We have developed an R package, seqTrun , for implementation of our method. 相似文献
Isolated microspore culture has been implemented in breeding programs to produce doubled haploid (DH) lines and thus accelerates the breeding process. However, low microspore embryogenesis frequency in flowering Chinese cabbage remains a key obstacle to the practical application of this technique. This study aimed to establish an efficient microspore culture protocol for flowering Chinese cabbage that would be applied for heterosis breeding. Microspores of five genotypes, 19AY05, 19AY06, 19AY10, 19AY12, and 19AY15, were successfully induced to produce embryos in NLN-13 medium. Microspores of two genotypes, 19AY05 and 19AY15, were cultivated in NLN-13 medium supplemented with different concentrations (0, 0.01, 0.05, 0.1, or 0.2 mg·L−1) of compound sodium nitrophenol (sodium nitrophenol, 5-nitrophenol) to enhance microspore embryogenesis and plant regeneration without an intervening callus phase. The results showed that 0.05 ~ 0.1 mg· L−1 sodium nitrophenol and 0.01 ~ 0.2 mg· L−1 of 5-nitrophenol significantly promoted the induction of microspore embryogenesis of two genotypes, and the best concentrations required for different genotypes are different. Moreover, 0.1 mg· L−1 sodium nitrophenol can significantly increase the plant regeneration rate of the two genetypes. The 5-nitrophenol at 0.01 mg·L−1 significantly increased rate of embryos directly convert to plant in 19AY15. In addition, the average doubled haploid rates in the five genotypes were close to 63%. Horticultural traits of DH lines from 19AY05 were identified and all of them were self-incompatible lines. They showed a high uniformity and consistency that can be directly used for hybrid breeding. Furthermore, the hybrid combination was prepared with the selected DH lines and the Guangdong nucleus genic sterile line GMS019 to screen the excellent hybrid combination for the flowering Chinese cabbage breeding program. This method accelerates the application of microspore culture in hybrid breeding of flowering Chinese cabbage.