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Systemic acquired resistance (SAR) is activated by local infection and confers enhanced resistance against subsequent pathogen invasion. Salicylic acid (SA) and N-hydroxypipecolic acid (NHP) are two key signaling molecules in SAR and their levels accumulate during SAR activation. Two members of plant-specific Calmodulin-Binding Protein 60 (CBP60) transcription factor family, CBP60g and SARD1, regulate the expression of biosynthetic genes of SA and NHP. CBP60g and SARD1 function as master regulators of plant immunity and their expression levels are tightly controlled. Although there are numerous reports on regulation of their expression, the specific mechanisms by which SARD1 and CBP60g respond to pathogen infection are not yet fully understood. This study identifies and characterizes the role of the LAZARUS 1 (LAZ1) and its homolog LAZ1H1 in plant immunity. A forward genetic screen was conducted in the sard1-1 mutant background to identify mutants with enhanced SAR-deficient phenotypes (sard mutants), leading to the discovery of sard6-1 , which maps to the LAZ1 gene. LAZ1 and its homolog LAZ1H1 were found to be positive regulators of SAR through regulating the expression of CBP60g and SARD1 as well as biosynthetic genes of SA and NHP. Furthermore, Overexpression of LAZ1 , LAZ1H1 and its homologs from Nicotiana benthamiana and potato enhanced resistance in N. benthamiana against Phytophthora pathogens. These findings indicate that LAZ1 and LAZ1H1 are evolutionarily conserved proteins that play critical roles in plant immunity. [ABSTRACT FROM AUTHOR]

Plant immune responses are mainly activated by two types of receptor. Pattern recognition receptors localized on the plasma membrane perceive extracellular microbial features, and nucleotide-binding leucine-rich repeat receptors (NLRs) recognize intracellular effector proteins from pathogens.sup.1. NLRs possessing amino-terminal Toll/interleukin-1 receptor (TIR) domains activate defence responses via the NADase activity of the TIR domain.sup.2,3. Here we report that activation of TIR signalling has a key role in pattern-triggered immunity (PTI) mediated by pattern recognition receptors. TIR signalling mutants exhibit attenuated PTI responses and decreased resistance against pathogens. Consistently, PTI is compromised in plants with reduced NLR levels. Treatment with the PTI elicitor flg22 or nlp20 rapidly induces many genes encoding TIR-domain-containing proteins, which is likely to be responsible for activating TIR signalling during PTI. Overall, our study reveals that activation of TIR signalling is an important mechanism for boosting plant defence during PTI. A study reveals that activation of Toll/interleukin-1 receptor signalling is an important mechanism for boosting plant defence during pattern-triggered immunity., Author(s): Hainan Tian [sup.1] , Zhongshou Wu [sup.1] [sup.2] , Siyu Chen [sup.1] [sup.3] [sup.4] , Kevin Ao [sup.1] [sup.2] , Weijie Huang [sup.1] , Hoda Yaghmaiean [sup.1] , Tongjun [...]

Summary: In this paper, BDF2 schemes combined with the finite element method are proposed to solve control constrained optimal parameter control problems governed by bilinear parabolic equations, where the control variable acts as a reaction coefficient. The discretize‐then‐optimize (DO) approach is adopted. First, the state equation is discretized and two different discrete formulas are utilized for the objective functional. Then, by using the Lagrange multiplier method, two fully discrete first‐order necessary optimality systems are deduced and named as DO1 and DO2 systems, respectively. It can be found that the optimize‐then‐discretize (OD) and discretize‐then‐optimize (DO) approaches coincide in the case of the DO2 system. Furthermore, a priori error estimates are derived for the state, co‐state and control variables of the DO2 system, which show that the DO2 system has second‐order accuracy in time. Finally, three numerical examples are presented to illustrate the theoretical findings. [ABSTRACT FROM AUTHOR]

Oomycetes are a group of filamentous microorganisms that include some of the biggest threats to food security and natural ecosystems. However, much of the molecular basis of the pathogenesis and the development in these organisms remains to be learned, largely due to shortage of efficient genetic manipulation methods. In this study, we developed modified transformation methods for two important oomycete species, Phytophthora infestans and Plasmopara viticola, that bring destructive damage in agricultural production. As part of the study, we established an improved Agrobacterium-mediated transformation (AMT) method by prokaryotic expression in Agrobacterium tumefaciens of AtVIP1 (VirE2-interacting protein 1), an Arabidopsis bZIP gene required for AMT but absent in oomycetes genomes. Using the new method, we achieved an increment in transformation efficiency in two P. infestans strains. We further obtained a positive GFP transformant of P. viticola using the modified AMT method. By combining this method with the CRISPR/Cas12a genome editing system, we successfully performed targeted mutagenesis and generated loss-of-function mutations in two P. infestans genes. We edited a MADS-box transcription factor-encoding gene and found that a homozygous mutation in MADS-box results in poor sporulation and significantly reduced virulence. Meanwhile, a single-copy avirulence effector-encoding gene Avr8 in P. infestans was targeted and the edited transformants were virulent on potato carrying the cognate resistance gene R8, suggesting that loss of Avr8 led to successful evasion of the host immune response by the pathogen. In summary, this study reports on a modified genetic transformation and genome editing system, providing a potential tool for accelerating molecular genetic studies not only in oomycetes, but also other microorganisms. Author summary: Oomycetes are a unique group of animal and plant pathogens that include some of the biggest threats to food security and natural ecosystems. However, much of the pathogenesis and development in these organisms remains to be learned, largely due to shortage of efficient genetic manipulation methods for a long time. In this manuscript, we developed modified Agrobacterium-mediated genetic transformation strategies for Phytophthora infestans, a notorious oomycete species that caused Irish Famine in the 19th century, and Plasmopara viticola, the causal agent of grapevine downy mildew that is known as a highly destructive disease of grapevines in all grape-growing areas of the world. Using prokaryotic expression of a plant protein in A. tumefaciens, we achieved considerable increase in transformation rate in different P. infestans strains, and also acquired one positive transformant of P. viticola, a oomycete species that is extremely hard-to-transform and cannot be grown as an axenic culture. Using our improved transformation protocol, combined with the CRISPR/Cas12a system, we performed genome editing and created loss-of-function alleles in P. infestans. In summary, our study reports on modified genetic transformation methods, for two important oomycete species, that have the potential to accelerate the molecular genetic study of many other microorganisms. [ABSTRACT FROM AUTHOR]

In this paper, we adopt the optimize‐then‐discretize approach to solve parabolic optimal Dirichlet boundary control problems. First, we derive the first‐order necessary optimality system, which includes the state, co‐state equations, and the optimality condition. Then, we propose Crank–Nicolson finite difference schemes to discretize the optimality system in 1D and 2D cases, respectively. In order to build the second‐order spatial approximation, we use the ghost points on the boundary in the schemes. We prove that the proposed schemes are unconditionally stable, compatible, and second‐order convergent in both time and space. To avoid solving the large coupled schemes directly, we use the iterative method. Finally, we present several numerical examples to validate our theoretical analysis. [ABSTRACT FROM AUTHOR]

Summary: When encountering microbial pathogens, plant cells can recognize danger signals derived from pathogens, activate plant immune responses and generate cell‐autonomous as well as non‐cell‐autonomous defense signaling molecules, which promotes defense responses at the infection site and in the neighboring cells. Meanwhile, local damages can result in the release of immunogenic signals including damage‐associated molecule patterns and phytocytokines, which also serve as danger signals to potentiate immune responses in cells surrounding the infection site. Activation of local defense responses further induces the production of long‐distance defense signals, which can move to distal tissue to activate systemic acquired resistance. In this review, we summarize current knowledge on various signaling molecules involved in short‐ and long‐distance defense signaling, and emphasize the roles of regulatory proteins involved in the processes. Significance Statement: This review summarizes current knowledge on short‐ and long‐distance defense signaling molecules, including damage‐associated molecular patterns (DAMPs), phytocytokines, salicylic acid and N‐hydroxypipecolic acid, and emphasize the roles of regulatory proteins involved in their production and perception as well as downstream defense responses. [ABSTRACT FROM AUTHOR]

This paper discusses numerical simulation of three-dimensional compressible contamination treatment from nuclear waste in porous media. The mathematical model includes five major unknowns, the pressure, Darcy velocity, brine, radionuclide and the temperature, determined by a parabolic equation, convection-dominated diffusion equations and the heat conductor equation. Considering the physical properties and the characters of equations, a mixed volume element with the characteristics is presented. For the flow equation, a conservative mixed volume element is used to obtain the pressure and Darcy velocity, and improves the accuracy of the latter. The characteristics could solve the convection dominated problems well and confirm the stability and accuracy at the front sharps, thus a characteristic mixed volume element is given for computing the concentrations and temperature. The composite procedures have the nature of conservation. Convergence analysis is discussed. Finally, an experimental system of partial differential equations is carried out and the feasibility and computational efficiency are illustrated. This method could solve such complicated problems well. [ABSTRACT FROM AUTHOR]

The plant defense hormone salicylic acid (SA) is perceived by two classes of receptors, NPR1 and NPR3/NPR4. They function in two parallel pathways to regulate SA-induced defense gene expression. To better understand the roles of the SA receptors in plant defense, we systematically analyzed their contributions to different aspects of Arabidopsis (Arabidopsis thaliana) plant immunity using the SA-insensitive npr1-1 npr4-4D double mutant. We found that perception of SA by NPR1 and NPR4 is required for activation of N -hydroxypipecolic acid biosynthesis, which is essential for inducing systemic acquired resistance. In addition, both pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) are severely compromised in the npr1-1 npr4-4D double mutant. Interestingly, the PTI and ETI attenuation in npr1-1 npr4-4D is more dramatic compared with the SA-induction deficient2-1 (sid2-1) mutant, suggesting that the perception of residual levels of SA in sid2-1 also contributes to immunity. Furthermore, NPR1 and NPR4 are involved in positive feedback amplification of SA biosynthesis and regulation of SA homeostasis through modifications including 5-hydroxylation and glycosylation. Thus, the SA receptors NPR1 and NPR4 play broad roles in plant immunity. [ABSTRACT FROM AUTHOR]

Abstract In this paper, two conservative and fourth-order compact finite difference schemes are proposed and analyzed for solving the regularized long wave (RLW) equation. The first compact finite difference scheme is two-level and nonlinear implicit. The second scheme is three-level and linearized implicit. Conservations of the discrete mass and energy, and unique solvability of the numerical solutions are proved. Convergence and unconditional stability are also derived without any restrictions on the grid ratios by using discrete energy method. The optimal error estimates in norm ‖ ⋅ ‖ and ‖ ⋅ ‖ L ∞ are of fourth-order and second-order accuracy for the spatial and temporal step sizes, respectively. Numerical examples are presented to simulate the collision of different solitary waves and support the theoretical analysis. [ABSTRACT FROM AUTHOR]

A sparse grid stochastic collocation method combined with discontinuous Galerkin method is developed for solving convection dominated diffusion optimal control problem with random coefficients. By the optimal control theory, an optimality system is obtained for the problem, which consists of a state equation, a co-state equation and an inequality. Based on finite dimensional noise assumption of random field, the random coefficients are assumed to have finite term expansions depending on a finite number of mutually independent random variables in the probability space. An approximation scheme is established by using a discontinuous Galerkin method for the physical space and a sparse grid stochastic collocation method based on the Smolyak construction for the probability space, which leads to the solution of uncoupled deterministic problems. A priori error estimates are derived for the state, co-state and control variables. Numerical experiments are presented to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

The three‐dimensional displacement of two‐phase flow in porous media is a preliminary problem of numerical simulation of energy science and mathematics. The mathematical model is formulated by a nonlinear system of partial differential equations to describe incompressible miscible case. The pressure is defined by an elliptic equation, and the concentration is defined by a convection‐dominated diffusion equation. The pressure generates Darcy velocity and controls the dynamic change of concentration. We adopt a conservative block‐centered scheme to approximate the pressure and Darcy velocity, and the accuracy of Darcy velocity is improved one order. We use a block‐centered upwind multistep method to solve the concentration, where the time derivative is approximated by multistep method, and the diffusion term and convection term are treated by a block‐centered scheme and an upwind scheme, respectively. The composite algorithm is effective to solve such a convection‐dominated problem, since numerical oscillation and dispersion are avoided and computational accuracy is improved. Block‐centered method is conservative, and the concentration and the adjoint function are computed simultaneously. This physical nature is important in numerical simulation of seepage fluid. Using the convergence theory and techniques of priori estimates, we derive optimal estimate error. Numerical experiments and data show the support and consistency of theoretical result. The argument in the present paper shows a powerful tool to solve the well‐known model problem. [ABSTRACT FROM AUTHOR]

Summary: Salicylic acid (SA) is an essential defence hormone in plants. Upon pathogen infection, induced biosynthesis of SA is mediated by Isochorismate synthase 1 (ICS1), whose gene transcription is controlled mainly through two redundant transcription factors, SAR Deficient 1 (SARD1) and Calmodulin‐binding protein 60‐like g (CBP60g). Although these master transcription factors regulate not only positive, but also negative regulators of immunity, how they control signaling events downstream of different immune receptors is unclear. Using autoimmune mutants activating immunity mediated by different receptors we show that, although the sard1 cbp60g double mutant almost fully suppresses the activation of defence mediated by suppressor of npr1‐1, constitutive 2 (snc2), it strikingly enhances snc1, which carries a gain‐of‐function mutation in an intracellular nucleotide‐binding leucine‐rich repeat (NLR) immune receptor. This negative regulation of immunity is achieved through the transcriptional regulation of negative regulators, such as Nudix hydrolase homolog 6 (NUDT6). Our study highlights the diverse roles, especially the negative ones, in the regulation of plant immunity by the two master immune transcription factors SARD1 and CBP60g. SARD1 and CBP60g are master transcription factors in plant immunity. We found that sard1 cbp60g strikingly enhances the autoimmune phenotypes of snc1 despite reducing defence hormone salicylic acid levels. This negative regulation of immunity is achieved mainly through the transcriptional regulation of negative regulators such as NUDT6, highlighting the diverse roles, especially the negative ones by SARD1 and CBP60g. [ABSTRACT FROM AUTHOR]