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Conopomorpha sinensis Bradley is a host-specific pest of Litchi chinensis and Euphoria longan. Here, we demonstrated that C. sinensis has evolved special physical and chemical mechanisms for host plant location that enable it to survive and reproduce. Females favored laying their eggs on the convex surface of litchi fruit that had particular volatile characteristics. Experiments using a H-type olfactometer showed that female C. sinensis were attracted to litchi flowers, tender shoots, immature fruits, and mature fruits, with the highest attraction rate to mature fruits (74.67 ± 2.31%). There were no significant differences in the attraction of male C. sinensis to different litchi tissues. Further oviposition preference tests using the pericarp, pulp, and seeds of mature litchi fruits revealed that female C. sinensis prefer to lay their eggs on the pericarp. Litchi volatiles were found to be important in attracting C. sinensis to fruits for oviposition. Analysis of volatiles from different litchi tissues by HS-SPME-GC-MS revealed 31 similar volatiles, some of which may be important in the oviposition preference choices of C. sinensis on litchi fruit.

Sperm nuclear migration during fertilization in Arabidopsis and rice has recently been found to be actin-dependent, but the driving force behind this actin cytoskeleton-dependent motion is unclear. Here, we confirmed that the actin-dependent sperm nuclei migration during fertilization is a conserved mechanism in plants. Using in vitro fertilization systems, we showed that a functional actin is also essential in maize and tobacco for sperm nuclei migration after gamete membrane fusion. Cytoskeleton depolymerization inhibitor treatments supported the view that sperm nuclei migration is actin-dependent but microtubule-independent in both egg cell and central cell during double fertilization. We further revealed that the actin-based motor myosin is not the driving force for sperm nuclear migration in maize and tobacco. The WASP-Arp2/3 complex signal cascade is shown here to be involved in the regulation of sperm nuclear migration in maize and tobacco. It is interesting that sperm nuclei migration within somatic cell also need WASP-Arp2/3 complex signal cascade and actin, suggesting that the mechanism of sperm nuclear migration is not gamete specific.

Kinesins comprise a superfamily of microtubule-based motor proteins involved in essential processes in plant development, but few kinesins have been functionally identified during seed development. Especially, few kinesins that regulate cell division during embryogenesis have been identified. Here we report the functional characterization of NtKRP, a motor protein of the kinesin-12 family. NtKRP is predominantly expressed in embryos and embryonic roots. NtKRP RNAi lines displayed reductions in cell numbers in the meristematic zone, in embryonic root length, and in mature embryo and seed sizes. Furthermore, we also show that CDKA;1 binds to NtKRP at the consensus phosphorylation sites and that the decreased cell numbers in NtKRP-silenced embryos are due to a delay in cell division cycle at the G2/M transition. In addition, binding between the cargo-binding tail domain of NtKRP and CDKA; 1 was also determined. Our results reveal a novel molecular pathway that regulates embryo/seed development and critical role of kinesin in temporal and spatial regulation of a specific issue of embryo developmental.

Ribosomal proteins are involved in numerous essential cell activities in plants. However, the regulatory role in specific plant developmental processes has not yet been fully elucidated. Here we identified the new ribosomal protein L18aB, which is specifically involved in sexual reproduction and plays a critical role in male gametophyte development and embryo pattern formation. In rpl18aB mutant plants, the mature pollen grains can germinate normally, but their competitiveness for growing in the style is significantly reduced. More interestingly, RPL18aB is required in early embryogenesis. rpl18aB embryos displayed irregular cell division orientations in the early pro-embryo and arrested at the globular stage with possible, secondary pattern formation defects. Further investigations revealed that the polar transportation of auxin is disturbed in the rpl18aB mutant embryos, which may explain the observed failure in embryo pattern formation. The cell type-specific complementation of RPL18aB in rpl18aB was not able to recover the phenotype, indicating that RPL18aB may play an essential role in early cell fate determination. This work unravels a novel role in embryo development for a ribosomal protein and provides insight into regulatory mechanism of early embryogenesis.

Maternal gene products deposited in the egg regulate early embryogenesis before activation of the embryonic genome in animals. While in higher plants, it is believed that genes of parental origin contribute to early embryogenesis. However, little is known regarding the particular processes in which genes of parental origin are involved during early embryogenesis. Previously, we found that the initiation of programmed cell death (PCD) in the suspensor of the embryo is regulated by the cystatin, NtCYS. Here, we confirmed that both parental transcripts contribute to PCD, but the relative expression level of the maternal NtCYS allele was much higher than that of the paternal allele in early embryos of tobacco interspecific hybrids. The expression level of the maternal NtCYS allele was decreased markedly, which was necessary for the initiation of PCD, while the paternal allele didn’t change. Interestingly, the pattern of PCD in the hybrid suspensor and the morphology of the hybrid suspensor were similar to those of the maternal parent. Our results suggest that NtCYS-mediated PCD initiation in the hybrid suspensor is likely controlled in a maternal dominant manner. This finding represents an example of the involvement of parental transcripts in a specific developmental event during early embryogenesis.