The kiwifruit (Actinidia chinensis) is an economically and nutritionally important fruit crop with remarkably high vitamin C content. Here we report the draft genome sequence of a heterozygous kiwifruit, assembled from ~140-fold next-generation sequencing data. The assembled genome has a total length of 616.1 Mb and contains 39,040 genes. Comparative genomic analysis reveals that the kiwifruit has undergone an ancient hexaploidization event (γ) shared by core eudicots and two more recent whole-genome duplication events. Both recent duplication events occurred after the divergence of kiwifruit from tomato and potato and have contributed to the neofunctionalization of genes involved in regulating important kiwifruit characteristics, such as fruit vitamin C, flavonoid and carotenoid metabolism. As the first sequenced species in the Ericales, the kiwifruit genome sequence provides a valuable resource not only for biological discovery and crop improvement but also for evolutionary and comparative genomics analysis, particularly in the asterid lineage.

Accumulating evidence shows that hydrogen sulfide (H(2)S) plays various physiological roles in plants, such as seed germination, root organogenesis, abiotic stress tolerance, and senescence of cut flowers. However, whether H(2)S participates in the regulation of ripening and senescence in postharvest fruits remains unknown. In the present study, the effect of H(2)S on postharvest shelf life and antioxidant metabolism in strawberry fruits was investigated. Fumigation with H(2)S gas released from the H(2)S donor NaHS prolonged postharvest shelf life of strawberry fruits in a dose-dependent manner. Strawberry fruits fumigated with various concentrations of H(2)S sustained significantly lower rot index, higher fruit firmness, and kept lower respiration intensity and polygalacturonase activities than controls. Further investigation showed that H(2)S treatment maintained higher activities of catalase, guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase and lower activities of lipoxygenase relative to untreated controls. H(2)S also reduced malondialdehyde, hydrogen peroxide, and superoxide anion to levels below control fruits during storage. Moreover, H(2)S treatment maintained higher contents of reducing sugars, soluble proteins, free amino acid, and endogenous H(2)S in fruits. We interpret these data as indicating that H(2)S plays an antioxidative role in prolonging postharvest shelf life of strawberry fruits.

In this report, we demonstrate that sodium hydrosulfide (NaHS), a hydrogen sulfide (H(2)S) donor, promoted adventitious root formation mediated by auxin and nitric oxide (NO). Application of the H(2)S donor to seedling cuttings of sweet potato (Ipomoea batatas L.) promoted the number and length of adventitious roots in a dose-dependent manner. It was also verified that H(2)S or HS(-) rather than other sulfur-containing components derived from NaHS could be attributed to the stimulation of adventitious root formation. A rapid increase in endogenous H(2)S, indole acetic acid (IAA) and NO were sequentially observed in shoot tips of sweet potato seedlings treated with HaHS. Further investigation showed that H(2)S-mediated root formation was alleviated by N-1-naphthylphthalamic acid (NPA), an IAA transport inhibitor, and 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), an NO scavenger. Similar phenomena in H(2)S donor-dependent root organogenesis were observed in both excised willow (Salix matsudana var. tortuosa Vilm) shoots and soybean (Glycine max L.) seedlings. These results indicated that the process of H(2)S-induced adventitious root formation was likely mediated by IAA and NO, and that H(2)S acts upstream of IAA and NO signal transduction pathways.

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The adoption of pest-resistant transgenic plants to reduce yield loss and pesticide utilization has been successful in the past three decades. Recently, transgenic plant expressing double-stranded RNA (dsRNA) targeting pest genes emerges as a promising strategy for improving pest resistance in crops. The steroid hormone, 20-hydroxyecdysone (20E), predominately controls insect molting via its nuclear receptor complex, EcR-USP. Here we report that pest resistance is improved in transgenic tobacco plants expressing dsRNA of EcR from the cotton bollworm, Helicoverpa armigera, a serious lepidopteran pest for a variety of crops. When H. armigera larvae were fed with the whole transgenic tobacco plants expressing EcR dsRNA, resistance to H. armigera was significantly improved in transgenic plants. Meanwhile, when H. armigera larvae were fed with leaves of transgenic tobacco plants expressing EcR dsRNA, its EcR mRNA level was dramatically decreased causing molting defects and larval lethality. In addition, the transgenic tobacco plants expressing H. armigera EcR dsRNA were also resistant to another lepidopteran pest, the beet armyworm, Spodoptera exigua, due to the high similarity in the nucleotide sequences of their EcR genes. This study provides additional evidence that transgenic plant expressing dsRNA targeting insect-associated genes is able to improve pest resistance.