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Perennial trees have a recurring annual cycle of wood formation in response to environmental fluctuations. However, the precise molecular mechanisms that regulate the seasonal formation of wood remain poorly understood. Our prior study indicates that VCM1 and VCM2 play a vital role in regulating the activity of the vascular cambium by controlling the auxin homoeostasis of the cambium zone in Populus. This study indicates that abscisic acid (ABA) affects the expression of VCM1 and VCM2, which display seasonal fluctuations in relation to photoperiod changes. ABA‐responsive transcription factors AREB4 and AREB13, which are predominantly expressed in stem secondary vascular tissue, bind to VCM1 and VCM2 promoters to induce their expression. Seasonal changes in the photoperiod affect the ABA amount, which is linked to auxin‐regulated cambium activity via the functions of VCM1 and VCM2. Thus, the study reveals that AREB4/AREB13‐VCM1/VCM2‐PIN5b acts as a molecular module connecting ABA and auxin signals to control vascular cambium activity in seasonal wood formation. [ABSTRACT FROM AUTHOR]

Rainfall–runoff simulation is the basis of basin flood forecasting and water resource planning. However, karst basins are highly nonhomogeneous. With the intermittent uplift of the Earth's crust, karst landscapes with large depressions and nonhomogeneous vertical orientations have developed in many places, with the surface being covered with depressional soil layers and surrounded by hills. Thus, the springs are recharged in various ways. To better represent the transformation relationship between rainfall, soil water, fissure water, and conduit water, we proposed a conceptual hydrological model called the karst Sacramento (KSAC) model to simulate the rainfall–runoff processes in karst basins. The model couples Sacramento (SAC) and tank models to simulate rainfall–runoff processes in the soil layer of karst depressions and exposed carbonate rock areas, respectively. The KSAC model was applied to the simulation of rainfall–runoff in the Yuquandong (YQD) karst spring basin in central China. The simulation results revealed that the proposed model achieves satisfactory performance in simulating hourly rainfall–runoff processes. The model was further applied to water cycle processes and water resource evaluation studies in the basin. A comparison of models revealed that depressions were more effective in regulating karst groundwater circulation processes. This study can improve our understanding of complex and variable hydrological processes that occur in karst basins. [ABSTRACT FROM AUTHOR]

Summary: Fusarium wilt is one of the most serious diseases affecting cotton. However, the pathogenesis and mechanism by which Fusarium oxysporum overcomes plant defence responses are unclear. Here, a new group D mitogen‐activated protein kinase (MAPK) gene, GhMPK20, was identified and functionally analysed in cotton. GhMPK20 expression was significantly induced by F. oxysporum. Virus‐induced gene silencing (VIGS) of GhMPK20 in cotton increased the tolerance to F. oxysporum, whereas ectopic GhMPK20 overexpression in Nicotiana benthamiana reduced F. oxysporum resistance via disruption of the salicylic acid (SA)‐mediated defence pathway. More importantly, an F. oxysporum‐induced MAPK cascade pathway composed of GhMKK4, GhMPK20 and GhWRKY40 was identified. VIGS of GhMKK4 and GhWRKY40 also enhanced F. oxysporum resistance in cotton, and the function of GhMKK4–GhMPK20 was shown to be essential for F. oxysporum‐induced GhWRKY40 expression. Together, our results indicate that the GhMKK4–GhMPK20–GhWRKY40 cascade in cotton plays an important role in the pathogenesis of F. oxysporum. This research broadens our knowledge of the negative role of the MAPK cascade in disease resistance in cotton and provides an important scientific basis for the formulation of Fusarium wilt prevention strategies. [ABSTRACT FROM AUTHOR]

Mitogen-activated protein kinase (MAPK) cascades play critical roles in signal transduction processes in eukaryotes. The MAPK kinases (MAPKKs) that link MAPKK kinases (MAPKKKs) and MAPKs are key components of MAPK cascades. However, the intricate regulatory mechanisms that control MAPKKs under drought stress conditions are not fully understood, especially in cotton (Gossypium hirsutum) Here, we isolated and characterized the cotton group B MAPKK gene GhMKK3 Overexpressing GhMKK3 in Nicotiana benthamiana enhanced tolerance to drought, and the results of RNA sequencing (RNA-seq) and quantitative real-time PCR (qRT-PCR) assays suggest that GhMKK3 plays an important role in responses to abiotic stresses by regulating stomatal responses and root hair growth. Further evidence demonstrated that overexpressing GhMKK3 promoted root growth and ABA-induced stomatal closure. In contrast, silencing GhMKK3 in cotton using virus-induced gene silencing (VIGS) resulted in the opposite phenotypes. More importantly, we identified an ABA- and drought-induced MAPK cascade that is composed of GhMKK3, GhMPK7 and GhPIP1 that compensates for deficiency in the MAPK cascade pathway in cotton under drought stress conditions. Together, these findings significantly improve our understanding of the mechanism by which GhMKK3 positively regulates drought stress responses., (© The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.)