Journal of Genetics and Genomics

Reviewer Acknowledgements

2012, 39(1): I-II. doi: 10.1016/S1673-8527(12)00009-4

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Editorial

Yongbiao Xue

2012, 39(1): 1-2. doi: 10.1016/j.jgg.2012.01.003

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Brassinosteroid Signaling and Application in Rice

Hongning Tong, Chengcai Chu

2012, 39(1): 3-9. doi: 10.1016/j.jgg.2011.12.001

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Combined approaches with genetics, biochemistry, and proteomics studies have greatly advanced our understanding of brassinosteroid (BR) signaling in Arabidopsis. However, in rice, a model plant of monocot and as well an important crop plant, BR signaling is not as well characterized as in Arabidopsis. Recent studies by forward and reverse genetics have identified a number of either conserved or specific components of rice BR signaling pathway, bringing new ideas into BR signaling regulation mechanisms. Genetic manipulation of BR level or BR sensitivity to improve rice yield has established the great significance of BR research achievements.

MicroRNAs and Type 2 Diabetes/Obesity

Mustafa Abdo Saif Dehwah, Aimin Xu, Qingyang Huang

2012, 39(1): 11-18. doi: 10.1016/j.jgg.2011.11.007

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MicroRNAs belong to a newly identified class of small non-coding RNAs that have been widely implicated in the fine-tuning of many physiological processes such as the pathogenesis of type 2 diabetes (T2D) and obesity. Microarray studies have highlighted an altered profile of miRNA expression in insulin target tissues in diabetic and obese models. Emerging evidences suggest that miRNAs play significant roles in insulin production, secretion and actions, as well as in diverse aspects of glucose homeostasis and adipocyte differentiation. The identification of tissue-specific miRNAs implicated in T2D and obesity might be useful for the future development of effective strategies for early diagnosis and therapeutic intervention of obesity-related medical complications.

TG-interacting Factor (TGIF) Downregulates SOX3 Gene Expression in the NT2/D1 Cell Line

Marija Mojsin, Jelena Popovic, Natasa Kovacevic Grujicic, Milena Stevanovic

2012, 39(1): 19-27. doi: 10.1016/j.jgg.2011.11.006

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SOX3 is a member of the Sox gene family implicated in brain formation and cognitive function. It is considered to be one of the earliest neural markers in vertebrates, playing a role in specifying neuronal fate. Recently, we have established the first link between TALE (three-amino-acid loop extension) proteins, PBX1 (pre-B-cell leukemia homeobox 1) and MEIS1 (myeloid ecotropic viral integration site 1 homologue), and the expression of the human SOX3 gene. Here we present the evidence that TGIF (TG-interacting factor) is an additional TALE superfamily member involved in the regulation of human SOX3 gene expression in NT2/D1 cells by direct interaction with the consensus binding site that is conserved in primate orthologue promoters. Functional analysis demonstrated that mutation of the TGIF binding site resulted in the activation of SOX3 promoter. TGIF overexpression downregulates SOX3 promoter activity and decreases endogenous SOX3 protein expression in both uninduced and retinoic acid (RA)-induced NT2/D1 cells. Up to now, this is the first transcription factor identified as a negative regulator of SOX3 gene expression. The obtained results further underscore the significance of TALE proteins as important transcriptional regulators ofSOX3 gene expression.

MicroRNA-125b Induces Cancer Cell Apoptosis Through Suppression of Bcl-2 Expression

Aihua Zhao, Quan Zeng, Xiaoyan Xie, Junnian Zhou, Wen Yue, Yali Li, Xuetao Pei

2012, 39(1): 29-35. doi: 10.1016/j.jgg.2011.12.003

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MicroRNAs (miRNAs) are small, noncoding RNAs which can often act as an oncogene or a tumor suppressor. Several miRNAs are associated with the development of hepatocellular carcinoma (HCC). We demonstrated that miR-125b significantly suppresses HCC cell proliferation and promotes apoptosis by inhibiting the gene expression of the anti-apoptotic protein, Bcl-2. Bioinformatic analysis indicated that the 3′UTR of Bcl-2 has binding sites for miR-125b. Luciferase reporter assay confirmed the ability of miR-125b to dramatically suppress Bcl-2 transcription, suggesting that Bcl-2 is a target gene for miR-125b. We concluded that miR-125b acts as a tumor suppressor in hepatic tumor development by targeting Bcl-2 and inducing cancer cell apoptosis.

Deletion of the Initial 45 Residues of ARR18 Induces Cytokinin Response in Arabidopsis

Yan Liang, Xingchun Wang, Sulei Hong, Yansha Li, Jianru Zuo

2012, 39(1): 37-46. doi: 10.1016/j.jgg.2011.12.004

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Abstract:
The plant hormone cytokinin plays important roles in various aspects of plant growth and development. Cytokinin signaling is mediated by a multistep phosphorelay similar to bacterial two-component system. Type-B ARRs lie at the end of the cytokinin signaling, typically mediating the output response. However, it is still unclear how type-B ARRs are regulated in response to cytokinin. Typical type-B ARR contains an N-terminal receiver domain and a C-terminal effector domain. In this study, we performed a genome-wild comparative analysis by overexpressing full length and C-terminal effector domain of seven representative type-B ARRs. Our results indicated that overexpression of C-terminal effector domain causes short primary roots and short hypocotyls without the addition of cytokinin, suggesting that the inhibitory role of the receiver domain in the activity of the effector domain is a common mechanism in type-B ARRs. To investigate how the receiver domain inhibits the activity of the effector domain, we performed a deletion analysis. We found that deletion of the initial 45 residues of ARR18 (the 45 residues from N-terminus) causes pleiotropic growth defects by directly inducing cytokinin responsive genes. Together, our results suggest that the initial 45 residues are critical for the inhibitory role of the receiver domain to the effector domain in ARR18.

Isolation and Functional Characterisation of the Genes Encoding Δ8-Sphingolipid Desaturase from Brassica rapa

Shu-Fen Li, Li-Ying Song, Wei-Bo Yin, Yu-Hong Chen, Liang Chen, Ji-Lin Li, Richard R.-C. Wang, Zan-Min Hu

2012, 39(1): 47-59. doi: 10.1016/j.jgg.2011.12.002

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Δ⁸-Sphingolipid desaturase is the key enzyme that catalyses desaturation at the C8 position of the long-chain base of sphingolipids in higher plants. There have been no previous studies on the genes encoding Δ⁸-sphingolipid desaturases in Brassica rapa. In this study, four genes encoding Δ⁸-sphingolipid desaturases from B. rapa were isolated and characterised. Phylogenetic analyses indicated that these genes could be divided into two groups: BrD8A, BrD8C and BrD8D in group I, and BrD8B in group II. The two groups of genes diverged before the separation of Arabidopsis and Brassica. Though the four genes shared a high sequence similarity, and their coding desaturases all located in endoplasmic reticulum, they exhibited distinct expression patterns. Heterologous expression in Saccharomyces cerevisiae revealed that BrD8A/B/C/D were functionally diverse Δ⁸-sphingolipid desaturases that catalyse different ratios of the two products 8(Z)- and 8(E)-C18-phytosphingenine. The aluminium tolerance of transgenic yeasts expressing BrD8A/B/C/D was enhanced compared with that of control cells. Expression of BrD8A in Arabidopsis changed the ratio of 8(Z):8(E)-C18-phytosphingenine in transgenic plants. The information reported here provides new insights into the biochemical functional diversity and evolutionary relationship of Δ⁸-sphingolipid desaturase in plants and lays a foundation for further investigation of the mechanism of 8(Z)- and 8(E)-C18-phytosphingenine biosynthesis.

2012 Vol. 39, No. 1