A male gametophyte, or pollen develops in the anther, and its development plays an important male reproductive process in flowering plants. A properly designed transgene construct can help to tailor transgene expression in plants by altering the expression strength, timing, and location. In this process, the promoter plays a pivotal role in controlling transgene expression. In this research, the promoter regions of rice anther/pollen-specific genes, named as OsMSP1 to OsMSP11,were selected from the microarray data sets covering 4 developmental stage of male gametophyte and then used for the construction of vector by Gateway cloning method and transformed into rice and Arabidopsis. All 11 promoters in rice and 9 in Arabidopsis were displayed as anther/pollen-specific/preferential genes by GUS assay and RT-PCR analysis. Three out of 11 promoters showed consistent results with published data. In this study, we demonstrated on eight new anther/pollen-specific or -preferential promoters (OsMSP1, OsMSP2, OsMSP3, OsMSP4, OsMSP5, OsMSP6, OsMSP8, and OsMSP9, which have not been reported before. Although the expression pattern of different genes active in pollen grains is diverse and complex, these experimental results would be helpful to understand the molecular mechanism of regulatory elements in rice microspore/pollen-specific genes.

Pollen development in flowering plants is regulated by a comprehensive pattern of genes. One way to produce hybrid rice based on nuclear male sterility is to find out firstly the potential promoters that function specifically in anthers since it is a specific site for transcription initiation and play key roles for the spatial and temporal expression of the genes. To implement this objective, we were selected promoter region of 16 genes based on the expression pattern of microarray and then those were introduced into the promoterless final destination vector which containing the GFP and GUS reporters genes. The resulting twelve vectors were transformed into monocotyledonous rice (Oryza sativa L) and a dicotyledonous Arabidopsis as heterologous system. Minimum 20 plants for each vector were analyzed by histochemical GUS assay at the flowering stage in Arabidopsis. 9 vectors out of 12 vectors constructed were expressed exclusively at the anther, especially in pollen, however one vector exhibited expression in stigma. For rice, T-DNA insertion were confirmed with specific primers in each promoter and GFP region. All T0 transgenic plants contained T-DNA insertion in their genome. This study would provide valuable information for biotechnological application for the induction of male sterility in plants.

The transport of nascent messenger RNA from the nucleus to the cytoplasm is mediated by the THO/TREX complex and is evolutionary conserved from yeast, metazoa and humans. However, in plants, it is still yet unclear if the similar mechanism of transport exists. Here we identified and characterized a mutant gene, AtTHO2, a putative Arabidopsis thaliana THO2 component protein, homologous to yeast THO2 of the THO/TREX pathway required for mRNA transport. The mutation from this gene resulted to various developmental defects that include semi-dwarfism and abnormal floral development which further leads to sterility. Gene expression analysis revealed that AtTHO2 is expressed in all organs and pollen developmental stages. In addition, the homozygote progeny of null mutants did not persist until mature stage. These results suggest an indispensable role of AtTHO2 in the development of Arabidopsis. Differential gen expression and silencing were also observed between the null mutants and wild type depending on T-DNA insertion. Furthermore, alternative splicing which was tightly linked with the THO/TREX pathways was also defective on AtTHO2 and null mutants. A similar pattern of defect in SR34a was observed in the AtTHO2 and null mutants. In terms of microRNA biosynthesis, no significant differences were seen on the wild-type and mutant plants; however this data should be validated. Thus this work provides some evidences that a similar THO/TREX complex exist in plants and gave a foundation for further studies on the mechanism of nuclear export in plants.

A diverse number of genes are involved in the floral transition and development to ensure the proper timing on the switch from vegetative to reproductive development in Arabiodopsis. MADS-box genes play a major role in floral development especially in the case of vernalization process, In this study we mapped a mutation in MAF5 encoding a MADS-domain protein which was reported to be up-regulated during vernalization and regulates flowering time. The mutant in MAF5 showed several pleiotropic phenotypes that includes semi-dwarfism, delayed senescence and abnormal pollen phenotype, High percentages of vacuolated and aborted pollen phenotype were observed in the mutant plant. Transmission efficiency showed that mutation from this gene was defective in both male and female gametes. Furthermore, gene expression analysis revealed that this gene was predominantly expressed in reproductive organs and gave a strong expression in the mature pollen which coincides with the defect in pollen phenotype. The results from this study provide some evidences on the additional role of MAF5 in pollen development however more specific approaches should be done to determine the specific stages of pollen development altered in this mutant.

Pollen development in flowering plants is regulated by a comprehensive pattern of genes. One way to produce hybrid rice based on nuclear male sterility is to find out firstly the potential promoters that function specifically in anthers since it is a specific site for transcription initiation and play key roles for the spatial and temporal expression of the genes. To implement this objective, we were selected promoter region of 16 genes based on the expression pattern of microarray and then those were introduced into the promoterless final destination vector which containing the GFP and GUS reporters genes. The resulting twelve vectors were transformed into monocotyledonous rice (Oryza sativa L) and a dicotyledonous Arabidopsis as heterologous system. Minimum 20 plants for each vector were analyzed by histochemical GUS assay at the flowering stage in Arabidopsis. 9 vectors out of 12 vectors constructed were expressed exclusively at the anther, especially in pollen, however one vector exhibited expression in stigma. For rice, T-DNA insertion were confirmed with specific primers in each promoter and GFP region. All T0 transgenic plants contained T-DNA insertion in their genome. This study would provide valuable information for biotechnological application for the induction of male sterility in plants.

The pollen grain is a unique tricellular structure suitable for the delivery of the sperm cells to the ovule. All nutrients required for microspore and pollen cell growth are derived by passage through the anther locule and secretion by the tapetum lining. During later stages the tapetum degenerates but contributes to produce pigments, waxes, lipids and proteins which form the pollen coat and function in signaling between male (pollen) and female (pistil) tissues. The development of both normal pollen and tapetum is necessary for the fertilization processes in rice and would be exploited for the induction of male-sterility which is very useful to improve economic value of crops. We aredeveloping new approaches using a conditional male-sterility for the F1 hybrid seed production in rice. The conventional three parental systems for F1 hybrid seed production requirethe following three lines: male-sterile line, maintainer line, and restorer line. In this system, a critical requirement is to maintain the male-sterile inbred lines. Here we suggest molecular approaches, in which the engineered male-sterile plants are generated by regulating endogenous hormonal balance through the loss-of-function of genes. We can expect the male-sterility can be restored by exogenous applications of hormones such as gibberellin or jasmonic acid. Based on two parental systems, we will address the answer onfollowing question: how can we maintain a male-sterile line producing 100% male-sterile progenies without a maintainer? This work was supported by grants from Crop Functional Genomics Center of the 21C Frontier Program (CG1517), RepublicKorea.