1-Aminocyclopropane-1-carboxylic acid (ACC) is a biosynthetic precursor of ethylene, a gaseous plant hormone which controls a myriad of aspects of development and stress adaptation in higher plants. Here, we identified a mutant in Arabidopsis thaliana , designated as ACC-resistant2 ( are2 ), displaying a dose-dependent resistance to exogenously applied ACC. Physiological analyses revealed that mutation of are2 impaired various aspects of exogenous ACC-induced ethylene responses, while not affecting sensitivity to other plant hormones during seedling development. Interestingly, the are2 mutant was normally sensitive to gaseous ethylene, compared with the wild type. Double mutant analysis showed that the ethylene-overproducing mutations, eto1 or eto3 , and the constitutive ethylene signaling mutation, ctr1 were epistatic to the are2 mutation. These results suggest that the are2 mutant is not defective in ethylene biosynthesis or ethylene signaling per se. Map-based cloning of ARE2 demonstrated that LYSINE HISTIDINE TRANSPORTER1 ( LHT1 ), encoding an amino acid transporter, is the gene responsible. An uptake experiment with radiolabeled ACC indicated that mutations of LHT1 reduced, albeit not completely, uptake of ACC. Further, we performed an amino acid competition assay and found that two amino acids, alanine and glycine, known as substrates of LHT1, could suppress the ACC-induced triple response in a LHT1-dependent way. Taken together, these results provide the first molecular genetic evidence supporting that a class of amino acid transporters including LHT1 takes part in transport of ACC, thereby influencing exogenous ACC-induced ethylene responses in A. thaliana .

A smoke-derived compound, karrikin (KAR), and an endogenous but as yet unidentified KARRIKIN INSENSITIVE2 (KAI2) ligand (KL) have been identified as chemical cues in higher plants that impact on multiple aspects of growth and development. Genetic screening of light-signaling mutants in Arabidopsis thaliana has identified a mutant designated as ply2 (pleiotropic long hypocotyl2) that has pleiotropic light-response defects. In this study, we used positional cloning to identify the molecular lesion of ply2 as a missense mutation of KAI2/HYPOSENSITIVE TO LIGHT, which causes a single amino acid substitution, Ala219Val. Physiological analysis and genetic epistasis analysis with the KL-signaling components MORE AXILLARY GROWTH2 (MAX2) and SUPPRESSOR OF MAX2 1 suggested that the pleiotropic phenotypes of the ply2 mutant can be ascribed to a defect in KL-signaling. Molecular and biochemical analyses revealed that the mutant KAI2^ply2 protein is impaired in its ligand-binding activity. In support of this conclusion, X-ray crystallography studies suggested that the KAI2^ply2 mutation not only results in a narrowed entrance gate for the ligand but also alters the structural flexibility of the helical lid domains. We discuss the structural implications of the Ala219 residue with regard to ligand-specific binding and signaling of KAI2, together with potential functions of KL-signaling in the context of the light-regulatory network in Arabidopsis thaliana.

A PACLOBUTRAZOL-RESISTANCE (PRE) gene family, consisting of six genes in Arabidopsis thaliana, encodes a group of helix-loop-helix proteins that act in the growth-promoting transcriptional network. To delineate the specific role of each of the PRE genes in organ growth, we took a reverse genetic approach by constructing high order pre loss-of-function mutants of Arabidopsis thaliana. In addition to dwarf vegetative growth, some double or high order pre mutants exhibited defective floral development, resulting in reduced fertility. While pre2pre5 is normally fertile, both pre2pre6 and pre5pre6 showed reduced fertility. Further, the reduced fertility was exacerbated in the pre2pre5pre6 mutant, indicative of the redundant and critical roles of these PREs. Self-pollination assay and scanning electron microscopy analysis showed that the sterility of pre2pre5pre6 was mainly ascribed to the reduced cell elongation of anther filament, limiting access of pollens to stigma. We found that the expression of a subset of flower-development related genes including ARGOS, IAA19, ACS8, and MYB24 was downregulated in the pre2pre5pre6 flowers. Given these results, we propose that PREs, with unequal functional redundancy, take part in the coordinated growth of floral organs, contributing to successful autogamous reproduction in Arabidopsis thaliana.

Previous crime prediction research focusing on regional characteristics is lacking in terms of the examination of physical characteristics of individual crime scenes. This study, therefore, presents a street crime prediction model by analysing streetscape features within an actual field of vision for a low-rise housing area in South Korea, which serves as a gauge for potential offenders to carry out crime. First, we performed logistic regression to analyse the correlation between street crime opportunities and the elements of streets to derive an equation for predicting street crime using selected variables. Next, we created a crime prediction map based on a geographic information system that contains attribute data on these physical characteristics and presented a street crime prediction model based on the derived prediction equation. Finally, to test the prediction model, we compared actual crime data from the selected area with the results obtained from the prediction model. The test results showed that the prediction model classified 11 out of 29 actual crime spots as crime occurrence; among the 312 non-crime spots, 257 were classified as non-crime occurrence. Based on these test results, we confirm that the occurrence of street crime is affected by the physical characteristics within the actual field of vision and discuss the improvement of the prediction model.

Significance: Seed dormancy is an important developmental trait for plants, which ensures seed germination under more favorable spatiotemporal environments. A smoke compound, 3,4,5-trimethylfuran-2( 5H )-one, which is called TMB for short, has been identified to inhibit seed germination in a still elusive way. Here, we presented several lines of evidence that TMB inhibits seed germination through the induction of physiological dormancy. Furthermore, by isolating TMB-resistant Arabidopsis mutants, we demonstrated that TMB RESISTANT1 , encoding a Raf-like kinase, is critically required for the TMB-induced seed dormancy. These results suggest the presence of a smoke sensory pathway that takes part in the multiple layers of the dormancy regulatory network in higher plants.

Light is an important environmental cue, causing a high degree of developmental plasticity in higher plants. The outcome of light-regulated developmental response is determined by not only photo-sensory systems but also endogenous physiological contexts in plants. KARRIKIN-INSENSITIVE2 (KAI2) functions as a receptor of karrikin and endogenous, as yet to be identified, KAI2 ligand (KL). The loss-of-function of KAI2 caused light-hyposensitive photomorphogenesis, affecting the expression light-responsive genes under the light conditions. However, it remains still unclear how KAI2-KL signaling interacts with light-signaling. Here, we show that the ply2 mutation, a severe loss-of-function allele of KAI2 affected the expression of a subset of light-responsive genes, irrespectively of light condition. The results implied that the overlapping set of light- and KAI2-responsive genes may serve as an integrating node between light- and KAI2-KL signaling. Further, the results of double mutant analyses between the ply2 mutant and mutants of CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1) or LONG HYPOCOTYL IN FAR-RED (HFR1) implicated that KAI2-KL signaling acts at downstream of COP1, largely independently of HFR1. Together, these results suggest that KAI2-KL signaling intersects with a subset of the light-regulatory network, by which plants adjust their photomorphogenic development.