Search

Soybean is a short-day plant and its flowering process can be reversed when switching from short-day to long-day conditions. Flowering reversion provides a useful system to study the flowering process in both forward and backward directions. In this study, we optimized a soybean flowering reversion system using a photoperiod-sensitive cultivar Zigongdongdou. Three types of terminal structures were found during flowering reversion: reversed terminal raceme (RTR), short terminal raceme (STR), and vegetative terminal (VT). The relative frequency of these terminal structures during flowering reversion under long day was dependent on the duration of the prior short day (SD) pretreatment. This process is phytochrome dependent and young plants were more susceptible to flowering reversion. Leaf removal increased the minimal SD period needed for the induction of STR. To demonstrate the application of this system, we studied the patterns of in situ expression of the GmNMH7 gene during flowering development and reversion. NMH7 family members encode MADS-box proteins and are unique in legume families since their expression can be detected in both developing flowers and nodules. In situ hybridization experiments using plants grown under different photoperiod cycles provided several lines of evidence supporting a close relationship between GmNMH7 gene expression and floral development in soybean. Furthermore, it seems that GmNMH7 may participate in flower development at different stages. Interestingly, the expression pattern of GmNMH7 in root nodules was also found to be regulated by photoperiod. These results support the notion that the photoperiod sensitive GmNMH7 gene may play multiple roles in growth and development in soybean.

Allene oxide synthase (AOS) is the first enzyme in the lipoxygenase pathway which leads to the formation of jasmonic acid (JA). A full length cDNA of TaAOS was cloned in winter wheat (Triticum aestivum L. cv. Jinghua No.3) seedlings. The open reading frame encompassed 1410 bp encoding a polypeptide of 470 amino acids with calculated molecular mass of 51.9 kD. Southern blot analysis suggested there are three copies of the gene in wheat genome. The TaAOS mRNA could be strongly induced by exogenous JA, and the highest level JA was observed after a 10 h induction. In situ RNA hybridization of seedling indicated preferential gene expression in young leaves, especially in the parenchyma cells around the vascular bundles, and the hybridization also showed that exogenous La(3+) could not suppress the expression of TaAOS induced by JA.

A vernalization-related gene VER2 was iso- lated from winter wheat (Triticum aestivum L.) using a differential screening approach. The deduced VER2 is a lectin-like protein of 300 amino acids, which contains the presence of a jacalin-like GWG domain. RNA in situ hybridization results demonstrated that VER2 gene expression is restricted to the marginal meristems of immature leaves in vernalized wheat seedlings. No hybridization signal was detected in the epidermal tis- sue and vascular bundles. However, ''devernalization'' resulted in the silencing of VER2 gene activity. The gene expression pattern of VER2 induced by jasmonate was similar to that induced by vernalization. Antisense inhibition of VER2 in transgenic wheat showed that heading and maturation time were delayed up to 6 weeks compared with non-transformed wheat and the pBI121empty-vector-transformed wheat. Tissue degen- eration at the top of the spike was also noticed in the antisense inhibited transgenic wheat. These results suggest that VER2 plays an important role in vernal- ization signaling and spike development in winter wheat.