Root-knot nematodes (RKN, Meloidogyne spp.) are one of the most harmful pests in agriculture. Pasteuria penetrans, an obligate hyperparasite of RKN, is an effective biological control agent. However, little is known about the molecular mechanisms of interaction between P. penetrans and the second-stage juvenile (J2) of Meloidogyne incognita. Here, we used transcriptome sequencing to characterise the differential expression profiles between control J2 of M. incognita and J2 encumbered by P. penetrans endospores. A total of 445 genes were found to be differentially expressed, including 406 up-regulated and 39 down-regulated genes. Thirty-seven putative immune-related genes encoding collagens, cytochrome P450, lysozymes and other active proteins were identified. Genes involved in the ‘biosynthesis of unsaturated fatty acids’ pathway and several core sets of immune effectors were up-regulated, indicating conserved immune mechanisms among different nematodes. Down-regulation of cytochrome P450-related genes might suggest a specific defence response of M. incognita encumbered by P. penetrans endospores.
Pasteuria penetrans is an obligate parasite of root-knot nematodes. Pepper (Piper nigrum) is one of the main economic crops in Hainan Island, China, and the incidence of root-knot diseases is high. The Pasteuria samples from 20 pepper fields of seven counties in Hainan Island were identified, and the results suggested that there were various P. penetrans populations in the same field but no obvious specificity among different regions. However, five strains appeared to be potentially novel species of the genus Pasteuria by 16S rRNA gene sequence analysis. Additionally, further study showed that a single nematode of Meloidogyne incognita and of M. javanica could be infected by different strains of P. penetrans, and the genetic diversities of P. penetrans between two different host species were found only in gyrB rather than 16S rRNA and sigE gene sequences. These findings will provide some theoretical underpinning for the research of obligate parasitism mechanism between root-knot nematodes and P. penetrans.
As a prominent illusion, the motion aftereffect (MAE) has traditionally been considered a visual phenomenon. Recent neuroimaging work has revealed increased activities in MT+ and decreased activities in vestibular regions during the MAE, supporting the notion of visual–vestibular interaction on the MAE. Since the head had to remain stationary in fMRI experiments, vestibular self-motion signals were absent in those studies. Accordingly, more direct evidence is still lacking in terms of whether and how vestibular signals modulate the MAE. By developing a virtual reality approach, the present study for the first time demonstrates that horizontal head rotation affects the perceived velocity of the MAE. We found that the MAE was predominantly perceived as moving faster when its direction was opposite to the direction of head rotation than when its direction was the same as head rotation. The magnitude of this effect was positively correlated with the velocity of head rotation. Similar result patterns were not observed for the real motion stimuli. Our findings support a ‘cross-modal bias’ hypothesis that after living in a multisensory environment long-term the brain develops a strong association between signals from the visual and vestibular pathways. Consequently, weak biasing visual signals in the associated direction can spontaneously emerge with the input of vestibular signals in the multisensory brain areas, substantially modulating the illusory visual motion represented in those areas as well. The hypothesis can also be used to explain other multisensory integration phenomena.
Natal dispersals are male-biased in most Old World monkey species, especially those that are polygynous. We examined patterns of male dispersal in golden snub-nosed monkeys, in which male offspring mainly disperse as juveniles from their natal one-male units (OMUs) to a bachelor group. However, out of a total of 112 male dispersals from 2001–2016, we documented six cases in which male offspring remained in their natal OMU until sub-adulthood. Based on monitoring of dispersal dynamics, we found that male offspring were more likely to delay dispersal if the tenure of leader males was lengthy. Social network analysis showed male offspring who delayed dispersal exhibited strong social relationships with each other and their OMU leader male but not with the females of their OMU. Our results suggest that the length of leader male tenure may affect natal male dispersal due to benefits to leader males accrued via intrasexual competition and kin selection.