Rice Stripe Virus Influences On The Embryonic Development Of Small Brown Planthopper

Rice stripe virus (RSV), the type member of the genus Tenuivirus, has been reported to cause serious rice stripe disease in rice fields in China and cause severe losses. RSV is transmitted mainly by the small brown planthopper (SBPH) Laodelphax striatellus Fallen in a persistent, circulative-propagative manner. It is very crucial for disease control to research the interactions between RSV and SBPH. Our laboratory preliminary study showed that RSV had an adverse effect on the viability of SBPH offspring, including that hatchability of Fi progeny from viruliferous SBPH declined, and developmental phase delayed. On the basis of preliminary results, SBPH eggs as the research object in this paper, the mechanisms that RSV influences on the development of SBPH offspring was analyzed from the angle of biology and molecular biology.For the phenomenon that RSV affects hatching of SBPH eggs, optical microscopy of eggs from viruliferous SBPH parents was performed. The results showed there were a number of developmental retardation or stunt eggs in rice sheaths. Moreover, some eggs were anomalous (such as diapausing, malformations, blackening and rotten), and these anomalous could not become smoothly nymphs through hatching period, which resulted in the decline in the hatchability of offspring.For investigation of RSV propagation in the eggs, total RNAs from virμliferous SBPH’s F1 eggs were extracted. Expression quantity variations of RSV CP gene were examined with real-time quantitative PCR. The results showed that the relative expression quantity of CP increased gradually in the viruliferous eggs along with egg development. Furthermore, the important nonstructural protein SP of RSV as symbol target was also detected for analyzing viral propagation. The results demonstrated that SP and RNP of RSV were both detected in viruliferous eggs, with the expected size of 21 kDa (SP) and 35 kDa (RNP), respectively. The above mentioned results sufficiently indicate that RSV can replicate and accumμlate in SBPH eggs during egg development.In order to reveal the reason that RSV affects hatching of SBPH offspring, viruliferous and non-virμliferous SBPH eggs as the research object, expression level variations of 17 embryonic development genes in eggs were analyzed via real-time PCR. The results, in comparison with non-virμliferous SBPH eggs, expression quantity of 6 genes (deaf1, atpa, chorp,fd64a, ddx1 and lar) significantly decreased in viruliferous SBPH eggs, and key genes Chorion peroxidase (chorp) involved in regulating embryonic development reduced 24-fold in viruliferous eggs, which suggests that RSV infection might suppress these genes expression. View of this, that normal expression of embryonic development genes in viruliferous SBPH eggs were directly affected by RSV infection, resulting in declining hatchability and delaying developmental phase of F1 eggs.