November 2011, Volume 53 Issue 11, Pages 846ĘC911.

Cover Caption: Evolution of Species in Tacca
About the cover: Species in the genus of Tacca exhibit diverse inflorescence morphology including conspicuous involucres with variable shapes, and filiform bracteoles. In this issue, Zhang et al. (pp 901ĘC911) reconstructed the molecular phylogeny of these species using five genes to examine the evolution of these traits. Species with showy involucres and bracteoles formed the most advanced clade, while ancestral Tacca had small and plain involucres and short bracteoles. This study proposed that the showy involucres and bracteoles may have functions beyond the pollinator attractor. The cover picture shows the ancestral T. leontopetaloides with small, plain involucres and short bracteoles.


          Cell and Developmental Biology
Defective Etioplasts Observed in Variegation Mutants May Reveal the Light-Independent Regulation of White/Yellow Sectors of Arabidopsis Leaves
Author: Wenjuan Wu, Nabil Elsheery, Qing Wei, Lingang Zhang and Jirong Huang
Journal of Integrative Plant Biology 2011 53(11): 846-857
Published Online: October 9, 2011
DOI: 10.1111/j.1744-7909.2011.01079.x

Leaf variegation resulting from nuclear gene mutations has been used as a model system to elucidate the molecular mechanisms of chloroplast development. Since most variegation genes also function in photosynthesis, it remains unknown whether their roles in photosynthesis and chloroplast development are distinct. Here, using the variegation mutant thylakoid formation1 (thf1) we show that variegation formation is light independent. It was found that slow and uneven chloroplast development in thf1 can be attributed to defects in etioplast development in darkness. Ultrastructural analysis showed the coexistence of plastids with or without prolamellar bodies (PLB) in cells of thf1, but not of WT. Although THF1 mutation leads to significant decreases in the levels of Pchlide and Pchllide oxidoreductase (POR) expression, genetic and 5-aminolevulinic acid (ALA)-feeding analysis did not reveal Pchlide or POR to be critical factors for etioplast formation in thf1. Northern blot analysis showed that plastid gene expression is dramatically reduced in thf1 compared with that in WT, particularly in the dark. Our results also indicate that chlorophyll biosynthesis and expression of plastidic genes are coordinately suppressed in thf1. Based on these results, we propose a model to explain leaf variegation formation from the plastid development perspective.

Wu W, Elsheery N,Wei Q, Zhang L, Huang J (2011) Defective etioplasts observed in variegation mutants may reveal the light-independent regulation of white/yellow sectors of arabidopsis leaves. J. Integr. Plant Biol. 53(11), 846–857.

Abstract (Browse 1567)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Metabolism and Biochemistry
Localisation of Seed Oil Body Proteins in Tobacco Protoplasts Reveals Specific Mechanisms of Protein Targeting to Leaf Lipid Droplets
Author: Stefania De Domenico, Stefania Bonsegna, Marcello Salvatore Lenucci, Palmiro Poltronieri, Gian Pietro Di Sansebastiano and Angelo Santino
Journal of Integrative Plant Biology 2011 53(11): 858-868
Published Online: September 26, 2011
DOI: 10.1111/j.1744-7909.2011.01077.x

Oleosin, caleosin and steroleosin are normally expressed in developing seed cells and are targeted to oil bodies. In the present work, the cDNA of each gene tagged with fluorescent proteins was transiently expressed into tobacco protoplasts and the fluorescent patterns observed by confocal laser scanning microscopy. Our results indicated clear differences in the endocellular localization of the three proteins. Oleosin and caleosin both share a common structure consisting of a central hydrophobic domain flanked by two hydrophilic domains and were correctly targeted to lipid droplets (LD), whereas steroleosin, characterized by an N-terminal oil body anchoring domain, was mainly retained in the endoplasmic reticulum (ER). Protoplast fractionation on sucrose gradients indicated that both oleosin and caleosin-green fluorescent protein (GFP) peaked at different fractions than where steroleosin-GFP or the ER marker binding immunoglobulin protein (BiP), were recovered. Chemical analysis confirmed the presence of triacylglycerols in one of the fractions where oleosin-GFP was recovered. Finally, only oleosin- and caleosin-GFP were able to reconstitute artificial oil bodies in the presence of triacylglycerols and phospholipids. Taken together, our results pointed out for the first time that leaf LDs can be separated by the ER and both oleosin or caleosin are selectively targeted due to the existence of selective mechanisms controlling protein association with these organelles.

De Domenico S, Bonsegna S, Lenucci MS, Poltronieri P, Di Sansebastiano GP, Santino A (2011) Localization of seed oil body proteins in tobacco protoplasts reveals specific mechanisms of protein targeting to leaf lipid droplets. J. Integr. Plant Biol. 53(11), 858–868.

Abstract (Browse 1573)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Plant-environmental Interactions
Rice Homeobox Transcription Factor HOX1a Positively Regulates Gibberellin Responses by Directly Suppressing EL1  
Author: Bi-Qing Wen, Mei-Qing Xing, Hua Zhang, Cheng Dai and Hong-Wei Xue
Journal of Integrative Plant Biology 2011 53(11): 869-878
Published Online: September 21, 2011
DOI: 10.1111/j.1744-7909.2011.01075.x

Homeobox transcription factors are involved in various aspects of plant development, including maintenance of the biosynthesis and signaling pathways of different hormones. However, few direct targets of homeobox proteins have been identified. We here show that overexpression of rice homeobox gene HOX1a resulted in enhanced gibberellin (GA) response, indicating a positive effect of HOX1a in GA signaling. HOX1a is induced by GA and encodes a homeobox transcription factor with transcription repression activity. In addition, HOX1a suppresses the transcription of early flowering1 (EL1), a negative regulator of GA signaling, and further electrophoretic mobility shift assay and chromatin immunoprecipitation analysis revealed that HOX1a directly bound to the promoter region of EL1 to suppress its expression and stimulate GA signaling. These results demonstrate that HOX1a functions as a positive regulator of GA signaling by suppressing EL1, providing informative hints on the study of GA signaling.

 Wen BQ, Xing MQ, Zhang H, Dai C, Xue HW (2011) Rice homeobox transcription factor HOX1a positively regulates giberellin responses by directly suppressing EL1. J. Integr. Plant Biol. 53(11), 869–878.

Abstract (Browse 2213)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Molecular Physiology
Conservation and Diversity of MicroRNA-associated Copper-regulatory Networks in Populus Trichocarpa  
Author: Shanfa Lu, Chenmin Yang and Vincent L. Chiang
Journal of Integrative Plant Biology 2011 53(11): 879-891
Published Online: October 20, 2011
DOI: 10.1111/j.1744-7909.2011.01080.x

Plants develop important regulatory networks to adapt to the frequently-changing availability of copper (Cu). However, little is known about miRNA-associated Cu-regulatory networks in plant species other than Arabidopsis. Here, we report that Cu-responsive miRNAs in Populus trichocarpa (Torr. & Gray) include not only conserved miR397, miR398 and miR408, but also Populus-specific miR1444, suggesting the conservation and diversity of Cu-responsive miRNAs in plants. Copper-associated suppression of mature miRNAs is in company with the up-regulation of their target genes encoding Cu-containing proteins in Populus. The targets include miR397-targeted PtLAC5, PtLAC6 and PtLAC110a, miR398-targeted PtCSD1, PtCSD2a and PtCSD2b, miR408-targeted PtPCL1, PtPCL2, PtPCL3 and PtLAC4, and miR1444-targeted PtPPO3 and PtPPO6. Consistently, P. trichocarpa miR408 promoter-directed GUS gene expression is down-regulated by Cu in transgenic tobacco plants. Cu-response elements (CuREs) are found in the promoters of Cu-responsive miRNA genes. We identified 34 SQUAMOSA-promoter binding protein-like (SPL) genes, of which 17 are full-length PtSPL proteins or partial sequences with at least 300 amino acids. Phylogenetic analysis indicates that PtSPL3 and PtSPL4 are CuRE-binding proteins controlling Cu-responsive gene expression. Cu appears to be not involved in the regulation of these transcription factors because neither PtSPL3 nor PtSPL4 is Cu-regulated and no CuRE exists in their promoters.

Lu S, Yang C, Chiang VL (2011) Conservation and diversity of microrna-associated copper-regulatory networks in Populus trichocarpa. J. Integr. Plant Biol. 53(11), 879–891.

Abstract (Browse 1811)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Plant Reproduction Biology
A Genetic Pathway for Tapetum Development and Function in Arabidopsis
Author: Jun Zhu, Yue Lou, Xiaofeng Xu and Zhong-Nan Yang
Journal of Integrative Plant Biology 2011 53(11): 892-900
Published Online: September 29, 2011
DOI: 10.1111/j.1744-7909.2011.01078.x

In anther development, tapetal cells take part in complex processes, including endomitosis and apoptosis (programmed cell death). The tapetum provides many of the proteins, lipids, polysaccharides and other molecules necessary for pollen development. Several transcription factors, including DYT1, TDF1, AMS, MS188 and MS1, have been reported to be essential for tapetum development and function in Arabidopsis thaliana. Here, we present a detailed cytological analysis of knockout mutants for these genes, along with an in situ RNA hybridization experiment and double mutant analysis showing that these transcription factors form a genetic pathway in tapetum development. DYT1, TDF1 and AMS function in early tapetum development, while MS188 and MS1 are important for late tapetum development. The genetic pathway revealed in this work facilitates further investigation of the function and molecular mechanisms of tapetum development in Arabidopsis.

Zhu J, Lou Y, Xu X, Yang ZN (2011) A genetic pathway for tapetum development and function in Arabidopsis. J. Integr. Plant Biol. 53(11), 892–900.

Abstract (Browse 2164)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Molecular Ecology and Evolution
Phylogeny and Evolution of Bracts and Bracteoles in Tacca (Dioscoreaceae)
Author: Ling Zhang, Hong-Tao Li, Lian-Ming Gao, Jun-Bo Yang, De-Zhu Li, Charles H. Cannon, Jin Chen and Qing-Jun Li
Journal of Integrative Plant Biology 2011 53(11): 901-911
Published Online: September 25, 2011
DOI: 10.1111/j.1744-7909.2011.01076.x

Most species in the genus Tacca (Dioscoreaceae) feature green to black purple, conspicuous inflorescence involucral bracts with variable shapes, motile filiform appendages (bracteoles), and diverse types of inflorescence morphology. To infer the evolution of these inflorescence traits, we reconstructed the molecular phylogeny of the genus, using DNA sequences from one nuclear, one mitochondrial, and three plastid loci (Internal Transcribed Spacer (ITS), atpA, rbcL, trnL-F, and trnH-psbA). Involucres and bracteoles characters were mapped onto the phylogeny to analyze the sequence of inflorescence trait evolution. In all analyses, species with showy involucres and bracteoles formed the most derived clade, while ancestral Tacca had small and plain involucres and short bracteoles, namely less conspicuous inflorescence structures. Two of the species with the most elaborate inflorescence morphologies (T. chantrieri in southeast China and T. integrifolia in Tibet), are predominantly self-pollinated, indicating that these conspicuous floral displays have other functions rather than pollinator attraction. We hypothesize that the motile bracteoles and involucres may facilitate selfing; display photosynthesis in the dim understory, and protect flowers from herbivory.

Zhang L, Li HT, Gao LM, Yang JB, Li DZ, Cannon CH, Chen J, Li QJ (2011) Phylogeny and evolution of bracts and bracteoles in Tacca (Dioscoreaceae). J. Integr. Plant Biol. 53(11), 901–911.

Abstract (Browse 2274)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
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