Dexiang Gu

Involvement of Jasmonate­ signaling pathway in the herbivore-induced rice plant defense

The expression patterns of eight defenserelated genes in the herbivore-infested and jasmonatetreated (jasmonic acid, JA and its derivative MeJA) rice leaves were analyzed using RT-PCR. The results showed thatSpodoptera litura Fabricius (Lepidoptera: Noctuidae) herbivory induced the expression of lipoxygenase (LOX) and allene oxide synthase (AOS) genes that are involved in the jasmonate-signaling pathway. Moreover,S. litura damage resulted in the expression of farnesyl pyrophosphate synthase (FPS), Bowman-birk proteinase inhibitor (BBPI), phenylalanine ammonia-lyase (PAL) and other rice defenserelated genes that were also induced by aqueous JA treatment or gaseous MeJA treatment. These indicated that in rice leaves, the JA-related signaling pathway was involved in theS. litura-induced chemical defense. Mechanical damage and brown planthopper (BPH),Nilaparvata lugens (Stål) (Homoptera: Delphacidae) damage induced the expression ofLOX gene, but both treatments did not induce the expression ofAOS gene. However, BPH damage induced the expression of acidic pathogen-related protein 1 (PR1a), Chitinase (PR-3), andPAL genes, which is involved in the salicylatesignaling pathway. It was suggested that salicylate-related signaling pathway or other pathways, rather than jasmonate-signaling pathway was involved in the BPH-induced rice plant defense.

Apoptosis of Spodoptera litura larval hemocytes induced by heavy metal zinc

By adding different amount of zinc into the artificial medium of the insect larvae, the zinc-induced apoptosis of the larvae haemocytes of the herbivorous insectSpodoptera litura Fabricius was investigated with flow cytometer. The results showed that the increase of zinc dose in the artificial feed led to the accumulations of zinc in the larval hemolymph and fat body, and more zinc was accumulated in fat body than in hemolymph. The apoptosis of hemocytes was significantly induced at high zinc concentration (1000 mg·kg−1) in the insect diet, and the apoptosis rate was 63.63%, which was remarkably higher than that at control and lower concentrations (50-500 mg·kg−1). This suggests that the high dose of zinc in the artificial diet ofS. litura larvae could induce the apoptosis of the larval hemocytes ofS. litura.

QUANTIFYING PREDATION BY UMMELIATA INSEC‐TICEPS BOES. ET STR. (ARANEAE: LINYPHIIDAE) ON RICE PLANTHOPPERS USING ELISA*

Abstract  An enzyme‐linked immunosorbent assay (ELISA) has been developed to quantify predation by Ummeliata insecticeps Boes. et Str. on rice planthoppers in paddy fields in Dasha Township, Guangdong Province. The assay was completely specific for rice planthopper materials. The detection periods for antigens after an adult of U. insecticeps had fed on three 3–5th instar nymphs of white‐back planthopper (WBPH), Sogatella furcifera (Horvath), and brown planthopper (BPH), Nilaparvata lugens (Stal), at room temperature were 96 h and 120 h, respectively. The proportion of individual species of predators scoring positive ranged from 19. 05% to 47. 34% for WBPH, and from 9. 25% to 66. 67% for BPH in the early rice season. Although the numbers of the rice planthoppers consumed by U. insecticeps increased with increasing prey densities, the predation rates declined. When rice planthopper densities were low, the predation rates were relatively high. This kind of predation can explain why the rice planthoppers have never reached outbreak levels in rice fields in Dasha Township since 1973.

Expression of the fusion protein recombinant human granulocyte-macrophage colony stimulating factor and leukemia inhibitory factor in a baculovirus vector system.

A fusion gene coding human granulocyte-macrophage colony stimulating factor (GM-CSF) and leukemia inhibitory factor (LIF) cDNAs was inserted into the transfer vector pSXIVVI+ X3 with the control of Syn and XIV promoters. The Sf9 cells (Spodoptera frugiperda) were co-transfected with the recombinant plasmid and TnNPV DNA (Trichoplusia ni nuclear polyhedrosis virus DNA). The fusion protein recombinant human granulocyte-macrophage colony stimulating factor (GM-CSF) and leukemia inhibitory factor (LIF) could be synthesized in cells infected with recombinant virus at a level of about 23% of their total cellular protein. Activity analysis of the fusion protein in infected cells revealed that it exhibited the dual activities of GM-CSF and LIF. Western blot analysis of the expressed fusion protein in infected larvae showed that the virus-mediated fusion protein, with a molecular weight of ∼35 kDa, is confirmed with immunoreactivity.