The expression of a new HD-Zip II gene, MSHB1, involving the inhibitory effect of thidiazuron on somatic embryogenic competence in alfalfa (Medicago sativa L. cv. Jinnan) callus

Homeodomain leucine zipper (HD-Zip) proteins play important roles in plant development. In this study, we not only identified and characterized a new HD-Zip II gene, designated as MSHB1 (HM114227), from alfalfa (Medicago sativa L. cv. Jinnan) callus treated with thidiazuron (TDZ) which reduced the embryogenic competence of the callus, but also presented the first evidence that MSHB1 is involved in the inhibitory effect of TDZ on somatic embryogenic competence in alfalfa callus. The full-length cDNA was 1,578 bp with an open reading frame of 1,023 bp, encoding a predicted protein of 340 amino acid residues, plus three introns. MSHB1 was strongly expressed in the callus treated with TDZ, but was only slightly detected in the leaf and petiole. TDZ treatment significantly decreased the frequency of somatic embryogenesis in the callus, but up-regulated MSHB1 expression during callus induction, callus maintenance and somatic embryo induction. These results suggest that the inhibitory effect of TDZ on embryogenic competence of alfalfa callus might be mediated by the regulation of MSHB1 expression.     

小黑杨HD-Zip转录因子家族生物信息学及应答盐胁迫分析

HD-Zip转录因子基因是植物中特有的一类蛋白家族,在植物生长发育和逆境应答胁迫过程中发挥重要作用。HD-Zip转录因子基因是由高度保守的同源异型结构域（HD）和亮氨酸拉链域（LZ）结构域构成的特殊结构模型。杨树HD-Zip转录因子家族共有63个基因,可被分为HD-ZipⅠ、HD-ZipⅡ、HD-ZipⅢ和HD-ZipⅣ四个亚家族。本文利用RNA-Seq分析了盐胁迫条件下HD-Zip基因家族在小黑杨根、茎、叶等不同组织的基因表达差异,从转录组水平揭示其应答胁迫环境的分子机制,结果表明,盐胁迫下在叶中有25个HD-Zip基因下调表达,21个基因上调表达;茎中有42个基因下调表达,11个基因上调表达;根中有26个基因下调表达,24个基因上调表达。另外,本文根据拟南芥HD-Zip转录因子家族基因的已知功能,预测了杨树HD-Zip转录因子同源基因的功能,并利用生物信息学方法分析了杨树HD-Zip转录因子蛋白序列的保守结构域、氨基酸组成和理化性质等,为进一步研究杨树HD-Zip转录因子基因功能提供参考。     

Potential target gene and protein interaction ofPimpinella brachycarpa HD-Zip protein, Phz4 by yeast two-hybrid system

The yeast two-hybrid system was used to investigate dimerization between proteins ofPhz2 andPhz4 clones of the homeodomain-leucine zipper family which were obtained by screening aPimpinella brachycarpa shoot-tip cDNA library. Assays showed that Phz4 formed a homo rather than a heterodimer with Phz2. In addition, we isolated cDNA clones,Phyb1, Phyb2, andPhyb3, that encode proteins interacting with Phz4. Although Phyb1 is not a HD-Zip protein, the activity of interaction between Phyb1 and Phz4 was, surprisingly, stronger than that of the homodimerization of Phz4. The analysis of interacting parts indicated that from 1 bp to 466 bp of Phyb1, there was no interaction with Phz4, but from 467 bp to 593 bp, interactions were found with the N-terminal and C-terminal regions, except for HD-Zip of Phz4. This region ofPhyb1 contained a nuclear localization signal. DNA-binding analysis showed that the Phz4 HD-Zip domain recognized the [T(C/G)ATTG] core sequence and the region containing the [TCATTG] motif, which is, in itself, a promoter in vitro.     

非洲菊微管相关蛋白基因GMAP65-1功能分析

微管相关蛋白在植物生长发育过程中发挥重要作用。利用反转录聚合酶链式反应(RT-PCR)和快速扩增cDNA末端(RACE)技术对非洲菊(Gerbera hybrida)体内微管相关蛋白GMAP65-1基因进行了克隆, 获得的基因全长1 883 bp, 包含 1 740 bp的完整开放阅读框(ORF)。表达模式研究表明, 该基因在非洲菊幼嫩的根、叶及花中均有较高的表达, 且受到赤霉素(GA)诱导显著上调。构建GMAP65-1超表达载体, 经异源转化拟南芥(Arabidopsis thaliana)后筛选获得纯合株系, 对纯合株系进行表型观察。结果表明, GMAP65-1超表达植株的叶片及花瓣面积增大, 暗示该基因参与叶片及花瓣的形态建成。研究结果为花卉分子育种提供了理论依据及基因资源。     

A novel rice PR10 protein, RSOsPR10, specifically induced in roots by biotic and abiotic stresses, possibly via the jasmonic acid signaling pathway

Plant roots have important roles not only in absorption of water and nutrients, but also in stress tolerance such as desiccation, salt, and low temperature. We have investigated stress-response proteins from rice roots using 2-dimensional polyacrylamide-gel electrophoresis and found a rice protein, RO-292, which was induced specifically in roots when 2-week-old rice seedlings were subjected to salt and drought stress. The full-length RO-292 cDNA was cloned, and was determined to encode a protein of 160 amino acid residues (16.9 kDa, pI 4.74). The deduced amino acid sequence showed high similarity to known rice PR10 proteins, OsPR10a/PBZ1 and OsPR10b. RO-292 mRNA accumulated rapidly upon drought, NaCl, jasmonic acid and probenazole, but not by exposure to low temperature or by abscisic acid and salicylic acid. The RO-292 gene was also up-regulated by infection with rice blast fungus. Interestingly, induction was observed almost exclusively in roots, thus we named the gene RSOsPR10 (root specific rice PR10). The present results indicate that RSOsPR10 is a novel rice PR10 protein, which is rapidly induced in roots by salt, drought stresses and blast fungus infection possibly through activation of the jasmonic acid signaling pathway, but not the abscisic acid and salicylic acid signaling pathway.     

cDNA encoding a wheat (Triticum aestivum cv. Chinese Spring) glycine-rich RNA-binding protein

A wheat cDNA encoding a glycine-rich RNA-binding protein, whGRP-1, was isolated. WhGRP-1 contains two conserved domains, the RNA-binding motif (RNP motif) combined with a series of glycine-rich imperfect repeats, characteristic of a conserved family of plant RNA-binding proteins. Northern analysis revealed that whGRP-1 mRNA accumulates to high levels in roots and to lower levels in leaves of wheat seedlings. whGRP-1 mRNA accumulation is not enhanced by exogenous abscisic acid in seedlings and accumulates to very high levels during wheat embryo development, showing a pattern different from that of the ABA-inducible wheat Em gene.     

一种拟南芥ZIP蛋白全长cDNA的克隆及表达

利用异质DNA探针 ,从拟南芥叶片cDNA文库中筛选到一个阳性cDNA克隆———AT10 3。DNA序列分析表明 ,其编码产物含有一个亮氨酸拉链结构域和一个核定位信号肽。GenBank数据库搜寻结果显示 ,AT10 3未与任何已知功能基因有同源性 ,但与裂叶牵牛PNZIP、集胞藻的一个ORF、紫菜的一个ORF ,构成了一个在进化上非常保守的含有亮氨酸拉链结构域的新家族 ,极有可能是一新的核基因转录因子。AT10 3是一个单拷贝基因 ,在叶片组织中强烈表达并受光调节     

Roles of OsCKI1, a rice casein kinase I, in root development and plant hormone sensitivity

Casein kinases are critical in cell division and differentiation across species. A rice cDNA fragment encoding a putative casein kinase I (CKI) was identified via cDNA macroarray under brassinosteroid (BR) treatment, and a 1939-bp full-length cDNA, OsCKI1, was isolated and found to encode a putative 463-aa protein. RT-PCR and Northern blot analysis indicated that OsCKI1 was constitutively expressed in various rice tissues and upregulated by treatments with BR and abscisic acid (ABA). Enzymatic assay of recombinant OsCKI1 proteins expressed in Escherichia coli showed that the protein was capable of phosphorylating casein. The physiological roles of OsCKI1 were studied through antisense transgenic approaches, and homozygous transgenic plants showed abnormal root development, including fewer lateral and adventitious roots, and shortened primary roots as a result of reduced cell elongation. Treatment of wild-type plants with CKI-7, a specific inhibitor of CKI, also confirmed these functions of OsCKI1. Interestingly, in transgenic and CKI-7-treated plants, exogenously supplied IAA could restore normal root development, and measurement of free IAA content in CKI-deficient primary and adventitious roots revealed altered auxin content, indicating that OsCKI1 is involved in auxin metabolism or that it may affect auxin levels. Transgenic plants were less sensitive than control plants to ABA or BR treatment during germination, suggesting that OsCKI1 may be involved in various hormone-signaling pathways. OsCKI1-GFP fusion studies revealed the localization of OsCKI1 to the nucleus, suggesting a possible involvement in regulation of gene expression. In OsCKI1-deficient plants, differential gene expression was investigated using cDNA chip technology, and results indicated that genes related to signal transduction and hormone metabolism were indeed with altered expression.     

Evolution of the class III HD-Zip gene family in land plants

Arabidopsis class III homeodomain-leucine zipper (HD-Zip III) proteins play overlapping, distinct, and antagonistic roles in key aspects of development that have evolved during land plant evolution. To better understand this gene family's role in plant evolution and development as well as to address broader questions of how duplicated genes functionally diversify, we investigated the evolutionary history of this gene family. Phylogenetic analyses including homologs from diverse land plants indicate that a gene duplication event before the angiosperm--gymnosperm split gave rise to two gene lineages that diversified during angiosperm plant radiation. Heterologous expression of an HD-Zip III gene from the nonvascular plant moss within the Arabidopsis HD-zip III revoluta mutant modified but did not complement the phenotype. Comparison of the expression domains of flowering and nonflowering plant homologs indicate an ancestral role in vascular development and organ initiation but not in specifying organ polarity, a prominent role for angiosperm homologs.