September 2010, Volume 52 Issue 9, Pages 774ĘC851.


Cover Caption: Sialyltransferase and Pollen Tube Growth
Sialyltransferases in animals are involved in the biosynthesis of sialylated glycoproteins and glycolipids. The functions of sialyltransferases in plants still remain unclear. The study of Deng et al. (pp 829-843) demonstrated that the sialyltransferases-like protein endoded by MGP2 is involved in pollen tube growth. The tetrad analysis (cover picture) showed that mutations in MGP2 did not influence the pollen morphology, but drastically impaired the germination and growth of the pollen tubes.

 

          Cell and Developmental Biology
The Cysteine Pairs in CLV2 are Not Necessary for Sensing the CLV3 Peptide in Shoot and Root Meristems
Author: Xiufen Song, Peng Guo, Chen Li, Chun-Ming Liu
Journal of Integrative Plant Biology 2010 52(9): 774-781
Published Online: June 21, 2010
DOI: 10.1111/j.1744-7909.2010.00978.x
      
    

Receptor-like proteins (RLPs) are involved in both plant defense and developmental processes. Previous genetic and biochemical studies show that the leucine-rich repeat (LRR) receptor-like protein CLAVATA2 (CLV2) functions together with CLAVATA1 (CLV1) and CORYNE (CRN) in Arabidopsis to limit the stem cell number in shoot apical meristem, while in root it acts with CRN to trigger a premature differentiation of the stem cells after sensing the exogenously applied peptides of CLV3p, CLE19p or CLE40p. It has been proposed that disulfide bonds might be formed through two cysteine pairs in the extracellular LRR domains of CLV1 and CLV2 to stabilize the receptor complex. Here we tested the hypothesis by replacing these cysteines with alanines and showed that depletions of one or both of the cysteine pairs do not hamper the function of CLV2 in SAM maintenance. In vitro peptide assay also showed that removal of the cysteine pairs did not affect the perception of CLV3 peptides in roots. These observations allow us to conclude that the formation of disulfide bonds is not needed for the function of CLV2.

Song X, Guo P, Li C, Liu CM (2010) The cysteine pairs in CLV2 are not necessary for sensing the CLV3 peptide in shoot and root meristems. J. Integr. Plant Biol. 52(9), 774–781.

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          Metabolism and Biochemistry
Fingerprinting Analysis of Saposhnikovia divaricata using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography
Author: Yue-Yang Xin, An-Jun Deng, Guan-Hua Du, Jin-Lan Zhang and Hai-Lin Qin
Journal of Integrative Plant Biology 2010 52(9): 782-792
Published Online: May 21, 2010
DOI: 10.1111/j.1744-7909.2010.00968.x
      
    

The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar and polar extracts (control substance for plant drug [CSPD] A and B) from the roots of 12 specimens of Saposhnikovia divaricata (Turcz.) Schischk were achieved with Fourier Transform (FT)-NMR spectrometer and assigned by comparison to each other and to the 1H NMR spectra of the isolated individual compounds. These fingerprints were found to be uniform in terms of the specificity for the implication of all 12 specimens being systematically of the same origin. The uniformity was further affirmed by high performance liquid chromatography (HPLC), which also revealed exactly identical specificity for the identified S. divaricata species with the 1H NMR appearances of corresponding CSPD on the part of the composition of characteristic constituents when comparing to corresponding individual compounds. This investigation unambiguously shows that the specific signals from the chemotaxonomically significant compounds of chromones and coumarins in S. divaricata are exhibited distinctively in the composite features of both 1H NMR fingerprints and HPLC profiles. The 1H NMR and HPLC profiles established can successfully be used as reference for the authentication of the origin of S. divaricata species as well as for chemotaxonomic studies.  

Xin YY, Deng AJ, Du GH, Zhang JL, Qin HL (2010) Fingerprinting analysis of Saposhnikovia divaricata using 1H nuclear magnetic resonance spectroscopy and high performance liquid chromatography. J. Integr. Plant Biol. 52(9), 782–792.

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Fast Isolation of Highly Active Photosystem II Core Complexes from Spinach
Author: Zhao-Gai Wang, Tian-Hua Xu, Cheng Liu and Chun-Hong Yang
Journal of Integrative Plant Biology 2010 52(9): 793-800
Published Online: May 26, 2010
DOI: 10.1111/j.1744-7909.2010.00971.x
      
    

Purification of photosystem II (PSII) core complexes is a time-consuming and low-efficiency process. In order to isolate pure and active PSII core complexes in large amounts, we have developed a fast method to isolate highly active monomeric and dimeric PSII core complexes from spinach leaves by using sucrose gradient ultracentrifugation. By using a vertical rotor the process was completed significantly faster compared with a swing-out rotor. In order to keep the core complexes in high activity, the whole isolation procedure was performed in the presence of glycine betain and pH at 6.3. The isolated pigment-protein complexes were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, absorption spectroscopy, 77 K fluorescence spectroscopy and high performance liquid chromatography. Our results show that this method is a better choice for quick and efficient isolation of functionally active PSII core complexes.

Wang ZG, Xu TH, Liu C, Yang CH (2010) Fast isolation of highly active photosystem II core complexes from spinach. J. Integr. Plant Biol. 52(9), 793–800.

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          Plant-environmental Interactions
Overexpression of AHL20 Negatively Regulates Defenses in Arabidopsis
Author: Haibin Lu, Yan Zou and Na Feng
Journal of Integrative Plant Biology 2010 52(9): 801-808
Published Online: May 20, 2010
DOI: 10.1111/j.1744-7909.2010.00969.x
      
    

Plants are equipped to recognize invading pathogenic microbes and activate innate immune responses by sensing pathogen-associated molecular patterns (PAMPs). PAMP-triggered immunity (PTI) is critical for plant resistance to potential pathogens. Although the mechanism by which PTI is activated has been intensively studied, how plants prevent unregulated immune responses is less well understood. Here we provide evidence that AHL20, an AT-hook containing DNA-binding protein, negatively regulates PTI. Overexpression of AHL20 as a stable transgene suppressed PAMP-induced NHO1 and FRK1 expression in Arabidopsis plants. Similarly, transient expression of the closely related family members AHL19, AHL15, and AHL27 in protoplasts also blocked PAMP-induced gene expression. The AHL20 overexpression plants displayed greater susceptibility to virulent P. syringae bacteria. These results indicate that AHL proteins play an important role in plant immunity.

Lu H, Zou Y, Feng N (2010) Overexpression of AHL20 negatively regulates defenses in Arabidopsis. J. Integr. Plant Biol. 52(9), 801–808.

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Light Regulation to Chlorophyll Synthesis and Plastid Development of the Chlorophyll-Less Golden-Leaf Privet
Author: Ming Yuan, Mo-Yun Xu, Shu Yuan, Yang-Er Chen, Jun-Bo Du, Fei Xu, Zhong-Wei Zhang, Zi-Chan Guo, Zhong-Yi Zhao and Hong-Hui Lin
Journal of Integrative Plant Biology 2010 52(9): 809-816
Published Online: June 29, 2010
DOI: 10.1111/j.1744-7909.2010.00979.x
      
    

Ligustrum vicaryi L. is a hybrid of Ligustrum ovalifolium Hassk. var. aureo-marginatum and Ligustrum
vulgale
L., and displays a chlorophyll-less phenotype. Therefore it is widely used as a horticultural shrub
because of its golden-color leaves. Its putative mechanism, light responses, chlorophyll synthesis and
plastid development were studied. L. vicaryi has a higher level of 5-aminolevulinic acid (ALA), but lower
levels of chlorophylls compared with L. quihoui. The yellowish phenotype of L. vicaryi upper leaves could
be attributed to their hampered conversion from chlorophyllide into chlorophyll a. Despite the enhanced
ALA level and the decreased thylakoid stacking in plastids, L. vicaryi golden leaves contain normal
levels of Lhcb transcripts and photosystem apoproteins. Furthermore, reactive oxygen species (ROS)
accumulation is almost the same in L. vicaryi and L. quihoui. The golden leaves often turn green and
the contents of chlorophylls increase with decreasing light intensity. Dynamic changes of chlorophyllsynthesis-
system under the light transition were also analyzed.

Yuan M, Xu MY, Yuan S, Chen YE, Du JB, Xu F, Zhang ZW, Guo ZC, Zhao ZY, Lin HH (2010) Light regulation to chlorophyll synthesis and plastid development of the chlorophyll-less golden-leaf privet. J. Integr. Plant Biol. 52(9), 809–816.

Abstract (Browse 2162)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Plant Reproduction Biology
SLOW WALKER3, Encoding a Putative DEAD-box RNA Helicase, is Essential for Female Gametogenesis in Arabidopsis  
Author: Man Liu, Dong-Qiao Shi, Li Yuan, Jie Liu and Wei-Cai Yang
Journal of Integrative Plant Biology 2010 52(9): 817-828
Published Online: June 4, 2010
DOI: 10.1111/j.1744-7909.2010.00972.x
      
    

RNA helicases are ATPases that unwind the secondary structures of RNAs and are required in almost any aspect of RNA metabolism. They are highly conserved from prokaryotic to eukaryotic organisms. However, their precise roles in plant physiology and development remain to be clarified. Here we report that the mutation in the gene SLOW WALKER3 (SWA3) results in the slow and retarded progression of mitosis during megagametogenesis in arabidopsis. SWA3 is a putative RNA helicase of DEAD-box subfamily. Mutant megagametophyte development is arrested at four- or eight-nucleate stages, furthermore, one of the synergids in about half of the mutant embryo sacs displays abnormal polarity, with its nucleus locating at the chalazal end, instead of the micropylar end in the wild-type. Transmission of the mutation through female gametophytes is severely reduced in swa3. However, a small portion of mutant embryo sacs are able to develop into mature and functional female gametophytes when pollination was postponed. The SWA3 in arabidopsis is a homologue of Dbp8 in yeast. Dbp8 interacts with Efs2 and is essential for biogenesis of 18S rRNA in yeast. Our data suggest that SWA3, may form complex with AtEfs2 and take roles in ribosomal biogenesis as RNA helicase during megagametogenesis in arabidopsis.

LiuM, Shi DQ, Yuan L, Liu J, YangWC(2010) SLOW WALKER3, encoding a putative DEAD-box RNA helicase, is essential for female gametogenesis in Arabidopsis. J. Integr. Plant Biol. 52(9), 817–828.

Abstract (Browse 2458)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
MALE GAMETOPHYTE DEFECTIVE 2, Encoding a Sialyltransferase-like Protein, is Required for Normal Pollen Germination and Pollen Tube Growth in Arabidopsis  
Author: Yi Deng, Wei Wang, Wen-Qing Li, Chuan Xia, Hong-Ze Liao, Xue-Qin Zhang and De Ye
Journal of Integrative Plant Biology 2010 52(9): 829-843
Published Online: July 16, 2010
DOI: 10.1111/j.1744-7909.2010.00963.x
      
    

Sialyltransferases (SiaTs) exist widely in vertebrates and play important roles in a variety of biological processes. In plants, several genes have also been identified to encode the proteins that share homology with the vertebrate SiaTs. However, very little is known about their functions in plants. Here we report the identification and characterization of a novel Arabidopsis gene, MALE GAMETOPHYTE DEFECTIVE 2 (MGP2) that encodes a sialyltransferase-like protein. MGP2 was expressed in all tissues including pollen grains and pollen tubes. The MGP2 protein was targeted to Golgi apparatus. Knockout of MGP2 significantly inhibited the pollen germination and retarded pollen tube growth in vitro and in vivo, but did not affect female gametophytic functions. These results suggest that the sialyltransferase-like protein MGP2 is important for normal pollen germination and pollen tube growth, giving a novel insight into the biological roles of the sialyltransferase-like proteins in plants.

Deng Y, Wang W, Li WQ, Xia C, Liao HZ, Zhang XQ, Ye D (2010) MALE GAMETOPHYTE DEFECTIVE 2 (MGP2), encoding a sialyltransferase-like protein, is required for normal pollen germination and pollen tube growth in Arabidopsis. J. Integr. Plant Biol. 52(9), 829–843.

Abstract (Browse 2573)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Molecular Ecology and Evolution
Natural Hybridization between Rhododendron delavayi and R. cyanocarpum (Ericaceae), from Morphological, Molecular and Reproductive Evidence
Author: Yong-Peng Ma, Chang-Qin Zhang, Jing-Li Zhang and Jun-Bo Yang
Journal of Integrative Plant Biology 2010 52(9): 844-851
Published Online: May 26, 2010
DOI: 10.1111/j.1744-7909.2010.00970.x
      
    

The natural hybridization that occurs between two sympatric species of Rhododendron subgenus Hymenanthes in Yunnan, China, was investigated. In field observations, it was noted that the putative hybrids between R. delavayi Franch. and R. cyanocarpum (Franch.) Franch. ex W.W. Sm. had intermediate morphologies. On the basis ofmorphology, chloroplast DNA (trnL-rpl32) and nuclear DNA (waxy), hybrids and parental species were identified. Hybridization occurred in both directions, but was asymmetrical, with R. delavayi as the major maternal parent. Reciprocal hand pollination treatments showed that either species, as pollen donor or pollen receiver, could produce fruits. It was noted that fruit set varied among treatments. The same pollinators (bumblebees) were shared in both parental species. From these results, we conclude that individuals with intermediate morphologies are indeed of hybrid origin from natural hybridization between R. cyanocarpum and R. delavayi. Furthermore, we presume the hybridization at the study site could have been initiated by habitat disturbance in the 1950s, and we may hence witness the early stages of hybrid swarm formation.

Ma YP, Zhang CQ, Zhang JL, Yang JB (2010) Natural hybridization between Rhododendron delavayi and R. cyanocarpum (Ericaceae), from morphological, molecular and reproductive evidence. J. Integr. Plant Biol. 52(9), 844–851.

Abstract (Browse 1926)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
 

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