Search

Eukaryotic translation initiation factor 4E1 (eIF4E1) is required for the initiation of protein synthesis. The biological function of eIF4E1 in plant–potyvirus interactions has been extensively studied. However, the role of eIF4E1 in Arabidopsis development remains unclear. In this study, we show that eIF4E1 is highly expressed in the embryo and root apical meristem. In addition, eIF4E1 expression is induced by auxin. eIF4E1 mutants show embryonic cell division defects and short primary roots, a result of reduced cell divisions. Furthermore, our results show that mutation in eIF4E1 severely reduces the accumulation of PIN-FORMED (PIN) proteins and decreases auxin-responsive gene expression at the root tip. Yeast two-hybrid assays identified that eIF4E1 interacts with an RAC/ROP GTPase activator, RopGEF7, which has been previously reported to be involved in the maintenance of the root apical meristem. The interaction between eIF4E1 and RopGEF7 is confirmed by protein pull-down and bimolecular fluorescent complementation assays in plant cells. Taken together, our results demonstrated that eIF4E1 is important for auxin-regulated embryo development and root growth. The eIF4E1–RopGEF7 interaction suggests that eIF4E1 may act through ROP signaling to regulate auxin transport, thus regulating auxin-dependent patterning.

Abstract Background RAC/ROP GTPase are versatile signaling molecules controlling diverse biological processes including cell polarity establishment, cell growth, morphogenesis, hormone responses and many other cellular processes in plants. The activities of ROPs are positively regulated by guanine nucleotide exchange factors (GEFs). Evidence suggests that RopGEFs regulate polar auxin transport and polar growth in pollen tube in Arabidopsis thaliana. However, the biological functions of rice RopGEFs during plant development remain largely unknown. Results We investigated a member of the OsRopGEF family, namely OsRopGEF7B. OsRopGEF7B pro :GUS analysis indicates that OsRopGEF7B is expressed in various tissues, especially in the floral meristem and floral organ primordia. Knock-out and -down of OsRopGEF7B by T-DNA insertion and RNA interference, respectively, predominantly caused an increase in the number of floral organs in the inner whorls (stamen and ovary), as well as abnormal paleae/lemmas and ectopic growth of lodicules, resulting in decline of rice seed setting. Bimolecular fluorescence complement (BiFC) assays as well as yeast two-hybrid assays indicate that OsRopGEF7B interacts with OsRACs. Conclusions OsRopGEF7B plays roles in floral organ development in rice, affecting rice seed setting rate. Manipulation of OsRopGEF7B has potential for application in genetically modified crops.

Polyamines not only play roles in plant growth and development, but also adapt to environmental stresses. Polyamines can be oxidized by copper-containing diamine oxidases (CuAOs) and flavin-containing polyamine oxidases (PAOs). Two types of PAOs exist in the plant kingdom; one type catalyzes the back conversion (BC-type) pathway and the other catalyzes the terminal catabolism (TC-type) pathway. The catabolic features and biological functions of plant PAOs have been investigated in various plants in the past years. In this review, we focus on the advance of PAO studies in rice, Arabidopsis, and tomato, and other plant species.

The stability of the core support barrel (CSB) in a nuclear reactor is the guarantee and premise for the normal operation of the reactor core. As the constraint and support of the CSB, the hold-down spring (HDS) directly affects the vibration characteristics of the CSB. Under harsh conditions such as high temperature and radiation, degradation such as stress relaxation may occur in terms of the performance of the HDS, which will affect the vibration of the CSB and the operation security of the reactor. Therefore, it is necessary to study the relaxation characteristics of the HDS of the CSB. First, a finite element model including the CSB and the HDS is established. The wet modal method is adapted to analyze and obtain the change of the beam mode frequency of the CSB with the relaxation degradation of the HDS. Then, a relaxation test of the HDS of the CSB is conducted to verify the simulation results. The simulation model is further used to generate more beam mode frequency data of the CSB under the impact of different relaxation degrees of the HDS. Finally, combined with simulation and test data, a mathematical model for identifying the relaxation degree of the HDS of the CSB is established, which lays a technical foundation for monitoring the relaxation and degradation of the HDS of the CSB in nuclear reactor.