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Pseudostellaria heterophylla, a valuable Chinese herbal medicine, is widely cultivated in China, with a planted area of 5402.7 hm2 in Shibing County, Guizhou Province. The occurrence of leaf spot disease represents a significant challenge in the production area. In this study, 30 samples of P. heterophylla exhibiting symptoms of leaf spot were collected from three primary production areas in Guizhou Province. Following isolation and purification, 51 isolates were classified into two genera based on both cultural and conidial characteristics, along with ITS sequence data. Fourteen representative strains were selected for morphological and multigene molecular identification, which revealed that these representative strains were affiliated with Alternaria arborescens species complex (SC), Alternaria tenuissima, Alternaria gaisen, and Sclerotiophoma versabilis. The isolation rates of Alternaria and Sclerotiophoma were 84.3% and 15.7%, respectively. Pathogenicity tests confirmed the identity of the causal agents and demonstrated varying levels of aggressiveness among the different genera and species of pathogens towards P. heterophylla leaves. This study marks the first identification of A. arborescens SC, A. gaisen, and S. versabilis as pathogens causing leaf spot in P. heterophylla in China. [ABSTRACT FROM AUTHOR]

The present study was designed to explore the role of soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP)/PKG pathway in sulfur dioxide (SO2)-induced vasodilation. We showed that SO2 induced a concentration-dependent relaxation of phenylephrine (PE)-precontracted rat aortic rings in association with an increase in cGMP concentration, whereas l-aspartic acid β-hydroxamate (HDX), an inhibitor of SO2 synthase, contracted rings in a dose-dependent manner. Pretreatment of aortic rings with the sGC inhibitor ODQ (30 μM) attenuated the vasodilatory effects of SO2, suggesting the involvement of cGMP pathway in SO2-induced vasodilation. Mechanistically, SO2 upregulated the protein levels of sGC and PKG dimers, while HDX inhibited it, indicating SO2 could promote cGMP synthesis through sGC activation. Furthermore, the dimerization of sGC and PKG and vasodilation induced by SO2 in precontracted rings were significantly prevented by thiol reductants dithiothreitol (DTT). In addition, SO2 reduced the activity of phosphodiesterase type 5 (PDE5), a cGMP-specific hydrolytic enzyme, implying that SO2 elevated cGMP concentration by inhibiting its hydrolysis. Hence, SO2 exerted its vasodilatory effects at least partly by promoting disulfide-dependent dimerization of sGC and PKG, resulting in an activated sGC/cGMP/PKG pathway in blood vessels. These findings revealed a new mode of action and mechanisms by which SO2 regulated the vascular tone., (Copyright © 2016 the American Physiological Society.)