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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]