In order to adapt to various environmental stresses, plants have employed diverse regulatory mechanisms of gene expression. Epigenetic changes, such as DNA methylation and histone modifications play an important role in gene expression regulation under stress condition. It has been known that some of epigenetic modifications are stably inherited after mitotic and meiotic cell divisions, which is known as stress memory. To understand molecular mechanisms underlying stress memory mediated by epigenetic modifications, we developed Arabidopsis suspension-cultured cell lines adapted to high salt by stepwise increases in the NaCl concentration up to 120 mM. Adapted cell line to 120 mM NaCl, named A120, exhibited enhanced salt tolerance compared to unadapted control cells (A0). Moreover, the salt tolerance of A120 cell line was stably maintained even in the absence of added NaCl, indicating that the salt tolerance of A120 cell line was memorized even after the stress is relieved. By using salt adapted and stress memorized cell lines, we intend to analyze the changes of DNA methylation, histone modification, transcriptome, and proteome to understand molecular mechanisms underlying stress adaptation as well as stress memory in plants.

FLOWERING LOCUS T (FT) is major determinant of the length of the vegetative phase in plants. To understand the role of FT homologs in flowering time control of soybean, we identified ten soybean FT genes and named GmFTs. Expression analysis of GmFT homologs showed that the transcripts of most FT clade genes are mainly expressed in leaves. The expression of GmFT2a, GmFT2b, GmFT5a, and GmFT6 strongly induced in response to floral inductive short-day condition, but GmFT4 and GmFT6 exhibited opposite expression pattern. To understand the biological function of each GmFT/TFL1 genes in flowering time control, we ectopically expressed GmFT cDNAs in Arabidopsis under the control of CaMV 35S promoter. Interestingly, while 35S:GmFT2a and 35S:GmFT5a transgenic plant showed extremely early flowering phenotype, overexpression of GmFT4 delayed flowering. Furthermore we analyzed expression patterns GmFT genes in the leaves of Korean soybean landraces showing various flowering time. The results showed that the transcript level of two FT homologs, GmFT2a and GmFT5a, was high in early flowering landraces, but low in late flowering landraces. In contrast, GmFT4 exhibited opposite expression pattern to those of GmFT2a and GmFT5a, suggesting that GmFT4 may function antagonistically to GmFT2a and GmFT5a in flowering time control of soybean. These results demonstrated that soybean FT homologs have both unique and conserved functions in the photoperiodic control of flowering compared with those in Arabidopsis.

Small RNAs including microRNAs (miRNAs) and small interfering RNAs (siRNAs) play crucial roles in post-transcriptional gene silencing (PTGS) in eukaryotes. Small RNAs function cell-autonomously as well as non-cell-autonomously. It has been well characterized that pathogenic fungi secrete some effector molecules, which facilitate their infection into plants. However, it is not clear whether molecules in plant cells are able to move into fungal cells during infection. To test if small RNAs generated from plant cells can also move to fungal cells during infection, we generated transgenic Arabidopsis and rice plants ectopically expressing either double-stranded RNA interference (dsRNAi) or artificial miRNA (amiRNA) constructs targeting GFP gene. And then these transgenic plants were inoculated with transgenic rice blast fungus, Magnaporthe oryzae, expressing GFP transgene. Here, we showed that ectopic expression of both dsRNAi and amiRNA targeting GFP gene in transgenic plants significantly suppressed GFP expression in rice blast fungi inoculated, indicating that small RNA molecules generated in plant cells can move into infected fungal cells and efficiently degrade fungal GFP transcripts. Our results would provide a new small RNA-based strategy for the development of resistant crops against fungal pathogens.