The Visual Object Tracking challenge VOT2019 is the seventh annual tracker benchmarking activity organized by the VOT initiative. Results of 81 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis as well as the standard VOT methodology for long-term tracking analysis. The VOT2019 challenge was composed of five challenges focusing on different tracking domains: (i) VOT-ST2019 challenge focused on short-term tracking in RGB, (ii) VOT-RT2019 challenge focused on "real-time" shortterm tracking in RGB, (iii) VOT-LT2019 focused on longterm tracking namely coping with target disappearance and reappearance. Two new challenges have been introduced: (iv) VOT-RGBT2019 challenge focused on short-term tracking in RGB and thermal imagery and (v) VOT-RGBD2019 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2019, VOT-RT2019 and VOT-LT2019 datasets were refreshed while new datasets were introduced for VOT-RGBT2019 and VOT-RGBD2019. The VOT toolkit has been updated to support both standard shortterm, long-term tracking and tracking with multi-channel imagery. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website 1 .

No abstract

Extracellular calmodulin (ExtCaM) regulates stomatal movement by eliciting a cascade of intracellular signaling events including heterotrimeric G protein, hydrogen peroxide (H 2 O 2 ), and Ca 2+ . However, the ExtCaM-mediated guard cell signaling pathway remains poorly understood. In this report, we show that Arabidopsis (Arabidopsis thaliana) NITRIC OXIDE ASSOCIATED1 (AtNOA1)-dependent nitric oxide (NO) accumulation plays a crucial role in ExtCaM-induced stomatal closure. ExtCaM triggered a significant increase in NO levels associated with stomatal closure in the wild type, but both effects were abolished in the Atnoa1 mutant. Furthermore, we found that ExtCaM-mediated NO generation is regulated by GPA1, the Ga-subunit of heterotrimeric G protein. The ExtCaM-dependent NO accumulation was nullified in gpa1 knockout mutants but enhanced by overexpression of a constitutively active form of GPA1 (cGa). In addition, cGa Atnoa1 and gpa1-2 Atnoa1 double mutants exhibited a similar response as did Atnoa1. The defect in gpa1 was rescued by overexpression of AtNOA1. Finally, we demonstrated that G protein activation of NO production depends on H 2 O 2 . Reduced H 2 O 2 levels in guard cells blocked the stomatal response of cGa lines, whereas exogenously applied H 2 O 2 rescued the defect in ExtCaM-mediated stomatal closure in gpa1 mutants. Moreover, the atrbohD/F mutant, which lacks the NADPH oxidase activity in guard cells, had impaired NO generation in response to ExtCaM, and H 2 O 2 -induced stomatal closure and NO accumulation were greatly impaired in Atnoa1. These findings have established a signaling pathway leading to ExtCaM-induced stomatal closure, which involves GPA1-dependent activation of H 2 O 2 production and subsequent AtNOA1-dependent NO accumulation.Plant guard cells control opening and closure of the stomata in response to phytohormones (e.g. abscisic acid [ABA]) and various environmental signals such as light and temperature, thereby regulating gas exchange for photosynthesis and water status via transpiration . Cytosolic calcium ([Ca 2+ ] i ) has been shown to be a key second messenger that changes in response to multiple stimuli in guard cells (McAinsh et al., 1995;Grabov and Blatt, 1998;Wood et al., 2000). A large proportion of Ca 2+ is localized in extracellular space. It has been shown that external Ca 2+ concentration ([Ca 2+ ] o ) promotes stomatal closure and induces oscillation in [Ca 2+ ] i in guard cells (MacRobbie, 1992;McAinsh et al., 1995;Allen et al., 2001 Calmodulin is a well-known Ca 2+ sensor that is activated upon binding of Ca 2+ . It has been shown that calmodulin exists not only intracellularly but also extracellularly in many plant species