Reactive oxygen and nitrogen species (ROS and RNS, respectively) are messengers that carry signals to alter the redox state in order to activate plant responses and other physiological processes, such as differentiation, aging, senescence, and pathogen defense. Quite a large number of genes are involved in this signaling and lead to oxidative stress in plants. Although the role of ROS/RNS during stress conditions is well documented, a comprehensive list of genes and comparative study of these genes has not yet been completed. Accordingly, the in silico identification of oxidative stress-related genes was performed for soybeans and Arabidopsis. These genes were also studied in relation to multiple domain prediction. The presence of domains like dehydogenase and ATPase suggests that these genes are involved in various metabolic processes, as well as the transportation of ions under optimal environmental conditions. In addition to a sequence analysis, a phylogenetic analysis was also performed to identify orthologous pairs among the soybean and Arabidopsis oxidative stress-related genes based on neighbor joining. This study was also conducted with the objective of further understanding the complex molecular signaling mechanism in plants under various stress conditions.

The objectives of this study were to investigate the diversity of natural products (DNP7, 9) in responding to Whitebacked planthopper (WBPH) feeding. Resistant rice (cv. Cheongcheong ), susceptible rice (cv. Nagdong) and susceptible control rice (cv. TN1) were used as materials for WBPH infestation in seedling stage. The treatment was conducted by spraying DNP 7 and 9 for 100 ppm to materials before being fed to 2nd and 3rd instar WBPH while control group was not sprayed DNP 7 and 9. The density of WBPH was 7 insect per plant. As a result, WBPH survival rate of 57% was found in the DNP 7 treatment, whereas those in DNP 9 and control were 27% and 71%, respectively. Resistance score of Cheongcheong, Nagdong, and TN1 in DNP 7 treatment were 3.4±0.8, 5.9±1.9, and 6.8±1.6, respectively, while those in DNP 9 treatment were 1.6±0.8, 4.7±1.6, and 7.9 ±1.4, respectively. The plant heights of Cheongcheong, Nagdong, and TN1 in DNP 7 treatment after 3 week infestation were 19.7±3.0, 23.4±7.5, and 15.8±8, respectively while those in DNP 9 treatment were 32.4±4, 26.3±12.7, and 25.9±8.5, respectively. Moreover, chlorophyll content was examined 3 week post infestation. In both DNP 7 and DNP 9 treatment, the chlorophyll levels of Cheongcheong and Nagdong in were higher than that in control. Based on observation and bio-scoring, plant with DNP 9 was strongly resistant to WBPH feeding and the survival rate of WHPB was lower than plant with DNP7.

Cambial meristematic cells (CMCs) are innately undifferentiated cells located in the meristems of plant with function as a stem cell to renew itself or replace specialized tissues. Another interesting feature of plant stem cells is controlling the plant defense in response to various stresses. Several groups have studied for stem cell triggered immunity signaling however, the molecular basis of the stem cell triggered immunity remains unclear. We previously obtained deferentially expressed 563 stem cell specific gene profiles from transcriptome analysis between two different cell types, CMC and dedifferentiated dells (DDCs) of yew tree (Taxuscuspidate). In a line of comparative genomics approach, we have selected 30 Arabidopsis homologous immune regulator candidate genes that showed significantly enriched GO terms ; at “response to stress” and “defense response”. We obtained one of homologous knock-out (KO) Arabidopsis mutant line on the locus At1G71110 whose cognate yew homologous gene showed predominantly expressed in CMCs compared to DDCs (20 times higher). For the assessment of basal disease resistance KO mutant plants were inoculated with Pseudomonas syringae pv. tomato (Pst) DC3000 and counted pathogen isolated from inoculated leaves. Interestingly, the KO mutant plants were not compromised in basal disease resistant, however, the hypersensitive response was significantly enhanced in the mutant compared to wild type in response to PstavrB, suggesting R-gene mediated defense response involved. We also investigated there sponse to the small reactive redox molecules such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) that associated significantly in plant immune response. Notably the KO mutant plants exhibited hypersensitivity specifically under nitrosative stress condition derived by S-nitrosiglutathione (GSNO), anitrioxide (NO) donor. Taken all together, putative endomembrane components At1G71110 may play a pivotal role in R gene mediated plant immune system. To further investigate its role(s) and molecular signaling network various defense gene expression profiles and functional genomics approach are ongoing for the long term aim of muti-stress tolerant crop development

Receptor mediated signal carriers play a critical role in regulation of plant defense and development. Rapid Alkalization Factor (RALF) is an important signaling family which has a role in plant growth and development. However, only few RALF polypeptides have been identified till date, mainly because of enormous efforts required for their isolation or identify their gene through mutational analysis. In this study, an extensive database search yield 39, 43, 34 and 23 potential RALF genes in Arabidopsis, rice, corn and soybeans, respectively. RALF genes are highly conserved across the plant species. A comprehensive analysis including the chromosomal location, gene structure, subcellular location, conserved motif, protein structure and promoter analysis was performed. RALF genes from four plants under study were divided in 7 groups based on phylogenetic analysis. In silico expression analysis of these genes, using microarray and EST data, reveled that these genes exhibit a variety of expression pattern. Furthermore, RALF genes showed distinct expression pattern under nitricoxide (NO) stress in Arabidopsis. This suggests a role of RALF genes in plant defense regulation. Our comprehensive analysis of RALF genes is a valuable resource that further elucidates the roles of RALF family members in plant growth and development. In addition, comparative genomics analyses deepen our understanding of the evolution of RALF gene family and will contribute to further genetics and genomics studies of other monocot and dicot plant species.