Valsa canker, caused by the fungus Valsa mali, is one of the most destructive diseases of apple trees in China and other East Asian countries. The plant receptorlike kinase FERONIA is involved in plant cell growth, development, and immunity. However, little is known about the function of FERONIA in apple defence against V. mali. In this study, we found that MdMRLK2 was highly induced by V. mali in twigs of V. mali-susceptible Malus mellana but not in those of the resistant species Malus yunnaensis. 35S:MdMRLK2 apple plants showed compromised resistance relative to wild-type (WT) plants. Further analyses indicated that 35S:MdMRLK2 apple plants had enhanced abscisic acid (ABA) levels and reduced salicylic acid (SA) levels relative to the WT on V. mali infection. MdMRLK2 overexpression also suppressed polyphenol accumulation and inhibited the activities of phenylalanine ammonia-lyase (PAL), β-1,3glucanase (GLU), and chitinase (CHT) during V. mali infection. Moreover, MdMRLK2 interacted with MdHIR1, a hypersensitive-induced response protein, and suppressed the MdHIR1-mediated hypersensitive reaction (HR), probably by impairing MdHIR1 self-interaction. Collectively, these findings demonstrate that overexpression of MdMRLK2 compromises Valsa canker resistance, probably by (a) altering ABA and SA levels, (b) suppressing polyphenol accumulation, (c) inhibiting PAL, GLU, and CHT activities, and (d) blocking MdHIR1-mediated HR by disrupting MdHIR1 self-interaction.
Drought is a major abiotic stress limiting the growth and production of apple trees worldwide. The receptor-like kinase FERONIA is involved in plant growth, development, and stress responses, however, the function of FERONIA in apple under drought stress remains unclear. Here, the FERONIA receptor kinase gene MdMRLK2 from apple (Malus domestica) was shown to encode a plasma membrane-localized transmembrane protein and was significantly induced by abscisic acid and drought treatments. 35S::MdMRLK2 apple plants showed less photosystem damage and higher photosynthetic rates compared with wild-type (WT) plants, after seven days withholding water. 35S::MdMRLK2 apple plants also had enhanced energy levels, activated caspase activity and more free amino acids, than the WT, under drought conditions. By performing yeast two-hybrid screening, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and MdCYS4, a member of cystatin, were identified as MdMRLK2 interaction partners. Moreover, under drought conditions, the 35S::MdMRLK2 apple plants were characterized by higher abscisic acid (ABA) content. Overall, these findings demonstrated that MdMRLK2 regulates apple drought tolerance, probably via regulating levels of energetic matters, free amino acids and ABA.
Simulation of complex scenarios and multi-direction pedestrian flow is a main challenge to microscopic model of pedestrian movement. It is an issue to simulate real pedestrian traffic with great fidelity while keeping its computational cost at an acceptable level. This paper reports on an improved floor field model called vector floor field model to simulate pedestrian flows in some basic scenarios. In this model, vectorization of static floor field and dynamic floor field are used to indicate preference directions and the pedestrian flow tendency, respectively. Pedestrian transition depends on both their preference directions and tendency. The simulations in some basic scenarios are conducted, quantitative comparison to the record of practical experiments and standard floor field model is given as well, and the results indicate the effectivity of this model. An adjusted static vector floor field is also proposed to simulate pedestrian flow in turning scenario. The vector floor field model is also sufficient to simulate some essential features in pedestrian dynamic, such as lane formation. This model can be widely used in the simulation of multi-direction pedestrian at turning, crossing and other junctions.
Osmotic adjustments play a fundamental role in plant responses to water deficit. For apple (Malus domestica) trees growing in the primary production areas of China, drought and low phosphorus (P) levels are the main sources of abiotic stress. Although tolerance to drought and low P are important breeding goals for cultivar improvement, there is little information on natural variation within Malus for these traits or the molecular mechanisms that may mediate tolerance. In this study, it was found that in plants grown under conditions of osmotic and low P stress, electrolyte leakage and photosynthetic parameters were significantly higher, but chlorophyll concentrations were lower compared with nonstressed plants. These physiological indicators revealed that, under low P condition, the order of osmotic stress resistance (high to low) was Malus sieversii (Ms) → Malus prunifolia (Mp) → Malus hupehensis (Mh). Expression of the phosphorus transporter genes PHT1;7, PHT1;12, and PHT2;1 in the roots and PHT1;12 and PHT4;5 in the leaves was positively correlated with plant osmotic resistance. It is proposed that the highly expressed PHT genes might improve P absorption and transport efficiency, resulting in the high osmotic stress resistance under low P level conditions in Malus species.
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