Os02g0641300

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Annotated Information

Function

MYB proteins are a superfamily of transcription factors that play regulatory roles in developmental processes and defense responses in plants(1). Relevant research indicated that the GAMyb is the sole GA-regulated transcription factor required for transcriptional activation of the high-pl a-amylase promoter. We therefore postulate that GAMyb is a part of the GA-response pathway leading to a-amylase gene expression in aleurone cells(3). In a transient transactivation experiment using Arabidopsis leaf protoplasts, researchers demonstrated that the ATMYB2 proteins activate transcription of the rd22 promoter fused to the β-glucuronidase reporter gene. This results indicate that the ATMYB2 (MYB) proteins function as transcriptional activators in the dehydration- and ABA-inducible expression of the rd22 gene(4).

Expression

The expression of the MYB genes were responsive to one or multiple types of hormone and stress treatments(1). Transient expression in protoplasts indicates that the upstream ORF inhibits expression of a downstream coding sequence. Reserachers have demonstrated that anoxia, in roots, increases the ratio between the spliced and the unspliced mRNA and affects the expression of othermyb-related genes(2). RNA blot analysis revealed that GAmyb expression in isolated barley aleurone layers is up-regulated by GA. The kinetics of GAmyb expression indicates that it is an early event in GA-regulated gene expression and precedes a-amylase gene expression(3).

Evolution

A phylogenetic comparison of the members of this superfamily in Arabidopsis and rice suggested that the Arabidopsis MYB superfamily underwent a rapid expansion after its divergence from monocots but before its divergence from other dicots. It is likely that the MYB-related family was more ancient than the R2R3-MYBgene family, or had evolved more rapidly. Therefore, the MYB gene superfamily represents an excellent system for investigating the evolution of large and complex gene families in higher plants(1). Relevant research reveal a remarkable excess of non-synonymous substitutions, an indication of adaptive selection on protein structure that occurred during the evolution of both helix1 and helix2 of rice R2R3-MYB DNA-binding domains. These flexible-helix regions associated with high frequencies of excess non-synonymous substitutions may play critical roles in the characteristic packing of R2R3-MYB DNA-binding domains and thereby modify the protein-DNA interaction process resulting in the recognition of novel DNA-binding sites. Furthermore, a co-evolutionary pattern is found between the second-helix of the R2 domain and the second-helix of the R3 domain by examining all the possible-helix pairings in both the R2 and R3 domains(5).

Labs working on this gene

(1)Peking–Yale Joint Center for Plant Molecular Genetics and AgroBiotechnology, National Key Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University ; College of Life Sciences, Peking University; Department of Molecular, Cellular and Developmental Biology, Yale University.

(2)Istituto Biosintesi Vegetali, C.N.R., Via Bassini 15, 20133 Milano, Italy

(3)Co-operative Research Centre for Plant Science, PO. Box 475, Canberra City, ACT, Australia

(4)Biological Resources Division, Japan lnternational Research Center for Agricultura1 Sciences (JIRCAS), Ministry of Agriculture, Forestry and Fisheries, 1-2 Ohwashi, Tsukuba, lbaraki 305, Japan.

(5)Department of Biological Sciences, Wichita State University, Wichita, Kansas 67260 (L.J.); Departments of Botany and Plant Science (M.T.C.) and Computer Science (T.J.), University of California, Riverside, California 92521

References

(1) Chen Yanhui , Yang Xiaoyuan,, He Kun,, Liu Meihua, Li Jigang, Gao Zhaofeng,Lin Zhiqiang,Zhang Yunfei, Wang Xiaoxiao, Qiu Xiaoming, Shen Yunping,Zhang Li, Deng Xiaohui, Luo Jingchu, Deng Xing-Wang, Chen Zhangliang,Gu Hongya, and Qu Li-Jia.The MYB transcription factor superfamily of Arabidopsis: expression analysis and phylogenetic comparison with the rice MYB family. Plant Molecular Biology (2006) 60:107–124 DOI 10.1007/s11103-005-2910-y

(2 ) Flavio Magaraggia, Giovanni Solina, Giorgio Valle, Giovanna Giovinazzo and Immacolata Coraggio. Maturation and translation mechanisms involved in the expression of a myb gene of rice. Plant Molecular Biology35:1003–1008, 1997.Kluwer Academic Publishers. Printed in Belgium

(3 ) Frank Gubler, Roger Kalla, James K. Roberts and John V. Jacobsen. The Plant Cell, Vol. 7, 1879-1891, November 1995 O 1995 American Society of Plant Physiologists.

(4) Hiroshi Abe, Kazuko Yamaguchi-Shinozaki, Takeshi Urao, Toshisuke lwasaki,C Daijiro Hosokawa,and Kazuo Shinozak. The Plant Cell, Vol. 9, 1859-1 868, October 1997 O 1997 American Society of Plant Physiologists.

(5) Li Jia, Michael T. Clegg, and Tao Jiang. Evolutionary Dynamics of the DNA-Binding Domains in Putative R2R3-MYB Genes Identified from Rice Subspeciesindica andjaponica Genomes Plant Physiology, February 2004, Vol. 134, pp. 575–585.