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Rice bc3 is one of the classical rice brittle culm mutants (Tanaka 1967), and has been used as a phenotype marker in rice genetic maps for breeding (Iwata and Omura 1977).
The expression pattern of the OsDRP2B gene in the tissues was analyzed by reporter gene assay using a Promoter OsDRP2B::β-glucuronidase (GUS) construct with 1,721 bp of upstream region of OsDRP2B. This construct was introduced into the wild-type cultivar Taichung 65. As the brittle phenotype was most obvious in the mature culms, we analyzed the GUS expression in three parts of the uppermost internode possessing a Xowering panicle (Fig. 1a). At the bottom of the internode adjacent to the node (the growing point where the culm is still young and soft), staining was conWned to the protoxylem tissue (Fig. 1b). Then, at the tissue 1–2 cm above the node, substantial and most active staining was seen in the developing cortical Wber cells, mainly adjacent to the developing cortical and small vascular bundles, and staining of the protoxylem tissue was weaker than the cortical Wber cells (Fig. 1c). At the top of the internode where the sclerenchyma was apparent, staining as seen only in the inner parts of the cortical Wber tissue that is seemingly at the completion stage of development (Fig. 1d). These expression patterns seem to correlate with the development of secondary walls of the cortical and vascular sclerenchymal Wber cells. As decreases in the cellulose fraction were also seen in the leaves, roots, and young seedlings of bc3 mutants, the expression of OsDRP2B promoter-GUS was also examined in these tissues (Fig. 2). Relatively strong GUS activity was observed mainly in the young tissues with active cell expansion. In leaves, at the youngest stage, GUS staining was observed in parenchymal tissue (Fig. 9a), and then shifted to the tracheal and phloem primordia in the young vascular bundles (Fig. 2b, c), but could not be detected at later stages. In roots, staining was observed at the very young stele (Fig. 2d) and at the bases of developing lateral roots (Fig. 2e). In mature anthers, GUS staining was also observed at the cortical layer and most strongly at the inner layer, which was considered to be the tapetum (Fig. 2f).
Figure.1 Developmental changes in the expression pattern of OsDRP2B promoter-GUS in the culm. a Scheme of the sectioned loci in a culm. b–d GUS staining of transverse sections of culms at the loci indicated in a. b GUS activity in the soft immature tissue near the basal developing point where cells are still lacking the developed sclerenchyma. c GUS activity in the slightly upper culm region compared to a. d GUS activity in the hard mature tissue. px protoxylem, cf cortical Wber cells.Bars 100 μm
Figure.2 Expression patterns of OsDRP2B in various rice tissues. a–c Transverse sections of leaves. a In the very young leaves. b In mature leaf tissues. Arrowheads show primordia of tracheae and phloem. c Higher magnification (×20) of the area circled in b. d Young roots. e Developing lateral roots. f Mature anther. tp tracheae primordium, pp phloem primordium. Bars 200 μm in a, 500 μm in b, d, e, and 100 μm in f
To determine the relationships of the OsDRP2B protein in the total dynamin family, a BLAST search was performed for all the rice dynamin-related proteins (OsDRPs) using OsDRP2B and human dynamin Dyn-1 sequences as queries and listed with Arabidopsis (At)DRPs (Hong et al. 2003) (Fig. 3). It is apparent that OsDRP2B, two Arabidopsis dynamins, and two additional rice classical dynamins constitute a group distinct from those other DRPs. It should be noted that none of the AtDRP2 mutants analyzed to date showed reductions in mechanical strength of the plant body. The 12 OsDRPs other than the three rice classical dynamins were categorized into AtDRPs groups that are based on their estimated association with mitochondria and chloroplasts, and sequence similarities with phragmoplastin and Mx-like proteins (Fig. 3). These results suggest that the various functions of these DRPs are conserved between the dicotyledonous and monocotyledonous plants, with the exception of two singletons of unknown function, AtDRP6 and OsDRP7. However, the 15 newly found OsDRPs did not show strict correspondence to the Arabidopsis counterparts within the subgroups and thus the terminal alphabetical IDs were given arbitrarily.
Figure3. Classification of rice DRPs based on Arabidopsis DRP subclasses. Analysis was performed by the neighbor-joining method, and the local bootstrap values (percentage) after 1,000 replicates are indicated near the branching points. Rice DRPs are shown in green and each was numbered in reference to the corresponding Arabidopsis DRPs
Labs working on this gene
1、State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences，Beijing 100101, China
2、State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences，Hangzhou 310006, China
3、National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences，Beijing 100081, China
4、National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan
5、Graduate School of Science and Engineering, Saitama University, Sakura-ku, Saitama 338-8570, Japan
6、Department of Science Education, Faculty of Education, Saitama University, Sakura-ku, Saitama 338-8570, Japan
7、Institute of Genetics and Developmental Biology; Chinese Academy of Sciences; Beijing, China
1、Ko Hirano, Toshihisa Kotake, Kumiko KamiharaRice et.al BRITTLE CULM 3 (BC3) encodes a classical dynamin OsDRP2B essential for proper secondary cell wall synthesis. Planta (2010) 232:95–108
2、Guangyan Xiong, Rui Li1, Qian Qian et.al The rice dynamin-related protein DRP2B mediates membrane trafficking, and thereby plays a critical role in secondary cell wall cellulose biosynthesis. The Plant Journal (2010) 64, 56–70
3、Rui Li, Guangyan Xiong , Yihua Zhou. Membrane trafficking mediated by OsDRP2B is specific for cellulose biosynthesis. Plant Signaling & Behavior 5:11, 1483-1486