Plant reproductive development begins when vegetative shoot apical meristems change their fate to inflorescence meristems which develop floral meristems on the flanks. This process of meristem fate change and organ development involves regulated activation and/or repression of many cell fate determining factors that execute down-stream gene expression cascades. Flowers are formed when floral organs are specified on the floral meristem in four concentric whorls. In the model dicot plant Arabidopsis, the identity and pattern of floral organs is determined by combined actions of MADS-domain containing transcription factors of the classes A, B, C, D and E. Rice florets are produced on a compact higher order branch of the inflorescence and have morphologically distinct non-reproductive organs that are positioned peripheral to the male and female reproductive organs. These unique outer organs are the lemma and palea that create a closed floret internal to which are a pair of lodicules that are asymmetrically positioned fleshy and reduced petal-like organs. The unique morphology of these rice floret organs pose intriguing questions on how evolutionary conserved floral meristem specifying and organ fate determining factors bring about their distinct developmental functions in rice. We have studied the functions for two rice MADS-box proteins, OsMADS2 and OsMADS1, to understand their role as master regulators of gene expression during rice floret meristem specification and organ development. OsMADS2; a transcriptional regulator of genes expression required for lodicule development Arabidopsis B-function genes AP3 and PI are stably expressed in the whorl 2 and 3 organ primordia and they together with other MADS-factors (Class A+E or C+E) regulate the differentiation of petals and stamens (Jack et al, 1992; Goto and Meyerowitz, 1994). Rice has a single AP3 ortholog, SPW1 (OsMADS16) but has duplicated PI-like genes, OsMADS2 and OsMADS4. Prior studies in our lab on one of these rice PI-like genes OsMADS2 showed that it is needed for lodicule development but is dispensable for stamen specification (Kang et al., 1998; Prasad and Vijayraghavan, 2003). Functional divergence between OsMADS2 and OsMADS4 may arise from protein divergence or from differences in their expression patterns within lodicule and stamen whorls. In this study, we have examined the dynamic expression pattern of both rice PI-like genes and have examined the likelihood of their functional redundancy for lodicule development. We show OsMADS2 transcripts occur at high levels in developing lodicules and transcripts are at reduced levels in stamens. In fully differentiated lodicules, OsMADS2 transcripts are more abundant in the distal and peripheral regions of lodicules, which are the tissues that are severely affected in OsMADS2 knock-down florets (Prasad and Vijayraghavan, 2003). The onset of OsMADS4 expression is in very young floret meristems before organ primordia emergence and this is expressed before OsMADS2. In florets undergoing organogenesis, high level OsMADS4 expression occurs in stamens and carpels and transcripts are at low level in lodicules (Yadav, Prasad and Vijayraghvan, 2007). Thus, we show that these paralogous genes differ in the onset of their activation and their stable transcript distribution within lodicules and stamens that are the conserved expression domains for PI-like genes. Since the expression of OsMADS4 in OsMADS2 knock-down florets is normal, our results show OsMADS2 has unique functions in lodicule development. Thus our data show subfunctionalization of these paralogous rice PI-like genes. To identify target genes regulated by OsMADS2 that could contribute to lodicule differentiation, we have adopted whole genome transcript analysis of wild-type and dsRNAiOsMADS2 panicles with developing florets. This analysis has identified potential down-stream targets of OsMADS2 many of which encode transcription factors, components of cell division cycle and signalling factors whose activities likely control lodicule differentiation. The expression levels of few candidate targets of OsMADS2 were examined in various floret organs. Further, the spatial expression pattern for four of these down-stream targets of OsMADS2 was analysed and we find overlap with OsMADS2 expression domains (Yadav, Prasad and Vijayraghvan, 2007). The predicted functions of these OsMADS2 target genes can explain the regulation of growth and unique vascular differentiation of this short fleshy modified petal analog. OsMADS1, a rice E-class gene, is a master regulator of other transcription factors and auxin and cytokinin signalling pathways In Arabidopsis four redundant SEPALLATA factors (E-class) are co-activators of other floral organ fate determining MADS-domain factors (classes ABCD) and thus contribute to floral meristem and floral organ development (Krizek and Fletcher, 2005). Among the grass-specific sub-clade of SEP-like genes, rice OsMADS1 is the best characterized. Prior studies in our lab showed that OsMADS1 is expressed early throughout the floret meristem before organ primordia emergence and later is restricted to the developing lemma and palea primordia with weak expression in carpel (Prasad et al, 2001). Stable expression continues in these floret organs. OsMADS1 plays critical non-redundant functions to specify a determinate floret meristem and also regulates floret organ identities (Jeon et al., 2000; Prasad et al, 2001; 2005; Agarwal et al., 2005; Chen et al., 2006). In the present study, we have adopted two different functional genomic approaches to identify genes down-stream of OsMADS1 in order to understand its mechanism of action during floret development. We have studied global transcript profiles in WT and dsRNAiOsMADS1 panicles and find OsMADS1 is a master regulator of a significant fraction of the genome’s transcription factors and also a number of genes involved in hormone-dependent cell signalling. We have validated few representative genes for transcription factors as targets regulated by OsMADS1. In a complementary approach, we have determined the consequences of induced-ectopic over-expression of a OsMADS1:ΔGR fusion protein in shoot apical meristems of transgenic plants. Transcript levels for candidate target genes were assessed in induced tissues and compared to mock-treated meristems and also with meristems induced for OsMADS1:ΔGR but blocked for new protein synthesis. These analyses show that OsMADS55 expression is directly regulated by OsMADS1. Importantly, OsMADS55 is related to SVP that plays an important role in floral transition and floral meristem identity in Arabidopsis. OsHB3 and OsHB4, homeodomain transcription factors, with a probable role in meristem function, are also directly regulated by OsMADS1. The regulation of such genes by OsMADS1 can explain its role in floret meristem specification. In addition to regulating other transcription factors, OsMADS1 knock-down affects expression of genes encoding proteins in various steps of auxin and cytokinin signalling pathways. Our differential expression profiling showed OsMADS1 positively regulates the auxin signalling pathway and negatively regulates cytokinin mediated signalling events. Through our induced ectopic expression studies of OsMADS1:ΔGR, we show OsMADS1 directly regulates the expression of OsETTIN2, an auxin response transcription factor, during floret development. Overall, we demonstrate that OsMADS1 modulates hormonal pathways to execute its functions during floret development on the spikelet meristems. Functional studies of OsMGH3; an auxin-responsive indirect target of OsMADS1 To better understand the contribution of auxin signalling during floret development, we have functionally characterized OsMGH3, a down-stream indirect target of OsMADS1, which is a member of the auxin-responsive GH3 family. The members of this family are direct targets of auxin response factors (ARF) class of transcription factors. GH3-proteins inactivate cellular auxin by conjugating them with amino acids and thus regulate auxin homeostasis in Arabidopsis (Staswick et al., 2005). OsMGH3 expression in rice florets overlaps with that of OsMADS1 (Prasad et al, 2005). In this study, we have demonstrated the consequences of OsMGH3 over-expression and knock-down. The over-expression of OsMGH3 during vegetative development causes auxin-deficient phenotypes such as dwarfism and loss of apical dominance. Its over-expression in developing panicles that was obtained by driving its expression from tissue-specific promoters created short panicles with reduced branching. The latter is a phenotype similar to that observed upon over-expression of OsMADS1. In contrast, the down-regulation of endogenous OsMGH3 through RNA-interference produced auxin over-production phenotypes such as ectopic rooting from aerial nodes. Knock-down of OsMGH3 expression in florets affected carpel development and pollen viability both of which affect floret fertility. Taken together, this study provides evidence for the importance of auxin homeostasis and its transcriptional regulation during rice panicle branching and floret organ development. Our analysis of various conserved transcription factors during rice floret development suggest that factors like OsMADS2, OsMADS4 and OsMADS1 are master regulators of gene expression during floret meristem specification and organ development. The target genes regulated by these factors contribute to development of morphologically distinct rice florets.

Genetic resources are important for the development of every country and for humanity. Collection, conservation and reasonable utilization of genetic resource is required mission. Understanding the importance of genetic resource, especially rice germplasm, since 2001, Center for conservation and development of crop genetic resources (CCD-CGR) of Hanoi University of Agriculture (Vietnam National University of Agriculture) has been collected, conserved and evaluated rice germplasm from different provinces of Vietnam for breeding programs. So far, 1090 accessions of local rice of Vietnam have been collected. Evaluation of agronomic properties and screening of some important genes using DNA molecular markers have revealed that Vietnamese rice germplasm has high level diversity and containing important genes for quality and resistance for disease and pests. These genetic resources are potential materials for national breeding programs. Based on the collected germplasm, 3 new glutinous rice varieties have been successfully created with high yield and good quality. In addition, the degradation of local rice varieties is also a matter of concern. So far, 4 specialty rice varieties Deo Dang, Ble chau, Pu de and Khau dao have been successfully restored for the north provinces of Vietnam. The main results of this study are germplasms for rice breeding programs and new improved varieties that bring economic benefits to farmers and the country. / Nguồn gene là tài nguyên sống còn của mỗi quốc gia và của toàn nhân loại. Vì vậy thu thập, bảo tồn, đánh giá và khai thác hợp lý nguồn tài nguyên này có ý nghĩa rất lớn. Nhận thức được tầm quan trọng của nguồn gen nhất là nguồn gen cây lúa, ngay từ đầu những năm 2000, Trung tâm bảo tồn và phát triển nguồn gene cây trồng thuộc Trường Đại học nông nghiệp, nay là Học Viện nông nghiệp Việt Nam đã tiến hành thu thập, lưu giữ, đánh giá và khai thác nguồn gene lúa. Kết quả đã thu thập, lưu giữ được 1090 mẫu giống lúa địa phương Việt Nam. Đánh giá đặc điểm nông sinh học và phát hiện một số gene quy định các tính trạng chất lượng và kháng sâu bệnh bằng chỉ thị phân tử DNA. Đây là nguồn gene quan trọng cho chọn tạo giống. Dựa vào nguồn gene thu thập được, cho đến nay, Trung tâm bảo tồn và phát triển nguồn gene cây trồng đã lai và chọn tạo được thành công 03 giống lúa nếp chất lượng cao. Ngoài ra, thoái hóa giống cũng là vấn đề đang được quan tâm. Cho đến nay 4 giống lúa đặc sản Đèo đàng, Ble châu, Pu đe và Khẩu dao đã được phục tráng và đưa vào sản xuất. Kết quả của những nghiên cứu này là ngân hàng các giống lúa làm nguồn gene để chọn tạo giống mới đem lại lợi ích kinh tế cho người nông dân và đất nước.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1963 D39 / Master of Science

LD2668 .T4 1966 S846 / Master of Science

Call number: LD2668 .T4 1978 C5 / Master of Science

Call number: LD2668 .T4 1978 W54 / Master of Science

Plant cells are routinely exposed to various pathogens and environmental stresses that cause cell wall perturbations. Little is known of the mechanisms that plant cells use to sense these disturbances and transduce corresponding signals to regulate cellular responses to maintain cell wall integrity. Previous studies in rice have shown that removal of the cell wall leads to substantial chromatin reorganization and histone modification changes concomitant with cell wall re-synthesis. But the genes and proteins that regulate these cellular responses are still largely unknown. Here we present an examination of the nuclear proteome differential expression in response to removal of the cell wall in rice suspension cells using multiple nuclear proteome extraction methods. A total of 382 nuclear proteins were identified with two or more peptides, including 26 transcription factors. Upon removal of the cell wall, 142 nuclear proteins were up regulated and 112 were down regulated. The differentially expressed proteins included transcription factors, histones, histone domain containing proteins, and histone modification enzymes. Gene ontology analysis of the differentially expressed proteins indicates that chromatin & nucleosome assembly, protein-DNA complex assembly, and DNA packaging are tightly associated with cell wall removal. Our results indicate that removal of the cell wall imposes a tremendous challenge to the cells. Consequently, plant cells respond to the removal of the cell wall in the nucleus at every level of the regulatory hierarchy.

BACKGROUND: Comparative evolutionary analysis of whole genomes requires not only accurate annotation of gene space, but also proper annotation of the repetitive fraction which is often the largest component of most if not all genomes larger than 50 kb in size. RESULTS: Here we present the Rice TE database (RiTE-db) - a genus-wide collection of transposable elements and repeated sequences across 11 diploid species of the genus Oryza and the closely-related out-group Leersia perrieri. The database consists of more than 170,000 entries divided into three main types: (i) a classified and curated set of publicly-available repeated sequences, (ii) a set of consensus assemblies of highly-repetitive sequences obtained from genome sequencing surveys of 12 species; and (iii) a set of full-length TEs, identified and extracted from 12 whole genome assemblies. CONCLUSIONS: This is the first report of a repeat dataset that spans the majority of repeat variability within an entire genus, and one that includes complete elements as well as unassembled repeats. The database allows sequence browsing, downloading, and similarity searches. Because of the strategy adopted, the RiTE-db opens a new path to unprecedented direct comparative studies that span the entire nuclear repeat content of 15 million years of Oryza diversity.