BackgroundPlants perceive UV-B through the UV RESISTANCE LOCUS 8 (UVR8) photoreceptor and UVR8 activation leads to changes in gene expression such as those associated with UV-B acclimation and stress tolerance. Albeit functionally unrelated, UVR8 shows some homology with RCC1 (Regulator of Chromatin Condensation 1) proteins from non-plant organisms at the sequence level. These proteins act as guanine nucleotide exchange factors for Ran GTPases and bind chromatin via histones. Subsequent to the revelation of this sequence homology, evidence was presented showing that UVR8 activity involves interaction with chromatin at the loci of some target genes through histone binding. This suggested a UVR8 mode-of-action intimately and directly linked with gene transcription. However, several aspects of UVR8 chromatin association remained undefined, namely the impact of UV-B on the process and how UVR8 chromatin association related to the transcription factor ELONGATED HYPOCOTYL 5 (HY5), which is important for UV-B signalling and has overlapping chromatin targets. Therefore, we have investigated UVR8 chromatin association in further detail.ResultsUnlike the claims of previous studies, our chromatin immunoprecipitation (ChIP) experiments do not confirm UVR8 chromatin association. In contrast to human RCC1, recombinant UVR8 also does not bind nucleosomes in vitro. Moreover, fusion of a VP16 activation domain to UVR8 did not alter expression of proposed UVR8 target genes in transient gene expression assays. Finally, comparison of the Drosophila DmRCC1 and the Arabidopsis UVR8 crystal structures revealed that critical histone- and DNA-interaction residues apparent in DmRCC1 are not conserved in UVR8.ConclusionThis has led us to conclude that the cellular activity of UVR8 likely does not involve its specific binding to chromatin at target genes.

BackgroundKernel weight and size are important components of grain yield in cereals. Although some information is available concerning the map positions of quantitative trait loci (QTL) for kernel weight and size in maize, little is known about the molecular mechanisms of these QTLs. qGW4.05 is a major QTL that is associated with kernel weight and size in maize. We combined linkage analysis and association mapping to fine-map and identify candidate gene(s) at qGW4.05.ResultsQTL qGW4.05 was fine-mapped to a 279.6-kb interval in a segregating population derived from a cross of Huangzaosi with LV28. By combining the results of regional association mapping and linkage analysis, we identified GRMZM2G039934 as a candidate gene responsible for qGW4.05. Candidate gene-based association mapping was conducted using a panel of 184 inbred lines with variable kernel weights and kernel sizes. Six polymorphic sites in the gene GRMZM2G039934 were significantly associated with kernel weight and kernel size.ConclusionThe results of linkage analysis and association mapping revealed that GRMZM2G039934 is the most likely candidate gene for qGW4.05. These results will improve our understanding of the genetic architecture and molecular mechanisms underlying kernel development in maize.

BackgroundChrysanthemum, a leading ornamental species, does not tolerate salinity stress, although some of its related species do. The current level of understanding regarding the mechanisms underlying salinity tolerance in this botanical group is still limited.ResultsA comparison of the physiological responses to salinity stress was made between Chrysanthemum morifolium ‘Jinba’ and its more tolerant relatives Crossostephium chinense, Artemisia japonica and Chrysanthemum crassum. The stress induced a higher accumulation of Na+ and more reduction of K+ in C. morifolium than in C. chinense, C. crassum and A. japonica, which also showed higher K+/Na+ ratio. Homologs of an Na+/H+ antiporter (SOS1) were isolated from each species. The gene carried by the tolerant plants were more strongly induced by salt stress than those carried by the non-tolerant ones. When expressed heterologously, they also conferred a greater degree of tolerance to a yeast mutant lacking Na+-pumping ATPase and plasma membrane Na+/H+ antiporter activity. The data suggested that the products of AjSOS1, CrcSOS1 and CcSOS1 functioned more effectively as Na+ excluders than those of CmSOS1. Over expression of four SOS1s improves the salinity tolerance of transgenic plants and the overexpressing plants of SOS1s from salt tolerant plants were more tolerant than that from salt sensitive plants. In addition, the importance of certain AjSOS1 residues for effective ion transport activity and salinity tolerance was established by site-directed mutagenesis and heterologous expression in yeast.ConclusionsAjSOS1, CrcSOS1 and CcSOS1 have potential as transgenes for enhancing salinity tolerance. Some of the mutations identified here may offer opportunities to better understand the mechanistic basis of salinity tolerance in the chrysanthemum complex.

BackgroundAlbumin 1b peptides (A1b) are small disulfide-knotted insecticidal peptides produced by Fabaceae (also called Leguminosae). To date, their diversity among this plant family has been essentially investigated through biochemical and PCR-based approaches. The availability of high-quality genomic resources for several fabaceae species, among which the model species Medicago truncatula (Mtr), allowed for a genomic analysis of this protein family aimed at i) deciphering the evolutionary history of A1b proteins and their links with A1b-nodulins that are short non-insecticidal disulfide-bonded peptides involved in root nodule signaling and ii) exploring the functional diversity of A1b for novel bioactive molecules.ResultsInvestigating the Mtr genome revealed a remarkable expansion, mainly through tandem duplications, of albumin1 (A1) genes, retaining nearly all of the same canonical structure at both gene and protein levels. Phylogenetic analysis revealed that the ancestral molecule was most probably insecticidal giving rise to, among others, A1b-nodulins. Expression meta-analysis revealed that many A1b coding genes are silent and a wide tissue distribution of the A1 transcripts/peptides within plant organs. Evolutionary rate analyses highlighted branches and sites with positive selection signatures, including two sites shown to be critical for insecticidal activity. Seven peptides were chemically synthesized and folded in vitro, then assayed for their biological activity. Among these, AG41 (aka MtrA1013 isoform, encoded by the orphan TA24778 contig.), showed an unexpectedly high insecticidal activity. The study highlights the unique burst of diversity of A1 peptides within the Medicago genus compared to the other taxa for which full-genomes are available: no A1 member in Lotus, or in red clover to date, while only a few are present in chick pea, soybean or pigeon pea genomes.ConclusionThe expansion of the A1 family in the Medicago genus is reminiscent of the situation described for another disulfide-rich peptide family, the “Nodule-specific Cysteine-Rich” (NCR), discovered within the same species. The oldest insecticidal A1b toxin was described from the Sophorae, dating the birth of this seed-defense function to more than 58 million years, and making this model of plant/insect toxin/receptor (A1b/insect v-ATPase) one of the oldest known.

contents01 The influence of soil salt content on the photosynthetic characteristics of spring wheat with trickle irrigationLei Pei, Zhenhua Wang, Jinzhu Zhang, Wenhao Li02 Comparing growth of fast-growing and slow-growing endophytes in plants via ergosterol quantificationAdeline SY Ting, Yiing Y Chow, Sadequr Rahman03 Transcriptome and digital gene expression analysis identifies putative triterpene saponin-biosynthetic genes of Panax notoginsengRongchang Wei04 Chitosan-assisted isolation and antioxidant evaluation of flavonoids from Sophora japonica L.Zhang Hu, Sidong Li, Chuyan Li, Zijuan Li05 Two kinds of new characteristics of the ektexine ornamentation of ginkgo pollenGuoxia Wang, Yuzhen Yang, Gang Chen, Qing Luo06 Analysis of nutrient and medicinal ingredients of Ginkgo pollen in different regionsGuoxia Wang, Ruixia Liu, Yuzhen Yang, Lipei Chen07 Photosynthetic performance of greening seedlings of seven species to drought stressZhiyang Lie, Tongtong Zhou, Weilong Huang, Li Xue08 Changes of fluorescence parameters of greening seedlings of seven species under drought stressJie Li, Zhuomin Wang, Li Xue09 Mammalian sex hormone affects regeneration capacity and enzymes activity of Triticale L in vitro cultureIsmail Bezirganoglu, Pınar Uysal10 Fractional Fourier entropy increases the recognition rate of fruit type detectionShuihua Wang, Zhihai Lu, Jiquan Yang, Yudong Zhang, John Liu, Ling Wei, Shufang Chen, Preetha Phillips, Zhengchao Dong11 Banana-peanut intercropping reduces Fusarium wilt disease in banana from enhancing soil bacterial microorganisms and leaf nutritionHong Li, Xutong Wang, Fengliang Zhao, Guisheng Yang12 Manganese stress impairs stem ureide nitrogen fixation in yardlong-bean plants in the acidic environmentHong Li13 A new pest control method for Rhytidodera bowringii LarvaeHaijie Huang, Li Zhao, Weijian Huang, Jinhui Wang, Zhongrun Zhang14 Research on the seed-like Fruits of Subg. Sclarea of Salvia of Labiatae in ChinaXiaojuan Li, Ning Xu, Guofu Zhou, Ming Wan, Qi Lin, Fanyun Meng, Jianxiu Li15 Three pulling resistance models of pioneer plant in landslide areaYichang Chen, Koayung Yu, Chunpin Chang16 The comparison of physiological and biochemical mechanisms of Reaumuria soongorica and Salsola passerine in different growth patternZijuan Zhou, Peixi Su, Rui Shi, Tingting Xie17 Resources use efficiency of the cosmopolitan plant Potentilla anserina L. in different alpine habitats in ChinaRui Shi, Peixi Su, Zijuan Zhou18 Cloning of PPDK gene from Red Amaranand transformation of AlfalfaXuelan Liu, Yan Zhang, Xiangfa Wei19 Variation and cluster analysis of morphological characters and nutrient content of Chucrasia tabularis seedChong Wu, Yanlei Yin, Lijuan Feng, Xuemei Yang, Fei Wang20 Effect of the planting density of the areca nut on the growth of intercropped VanillaHua Wang, Huifa Zhuang, Zihui Zhu, Hui Wang

BackgroundImprovement of freezing tolerance of red clover (Trifolium pratense L.) would increase its persistence under cold climate. In this study, we assessed the freezing tolerance and compared the proteome composition of non-acclimated and cold-acclimated plants of two initial cultivars of red clover: Endure (E-TF0) and Christie (C-TF0) and of populations issued from these cultivars after three (TF3) and four (TF4) cycles of phenotypic recurrent selection for superior freezing tolerance. Through this approach, we wanted to identify proteins that are associated with the improvement of freezing tolerance in red clover.ResultsFreezing tolerance expressed as the lethal temperature for 50 % of the plants (LT50) increased markedly from approximately −2 to −16 °C following cold acclimation. Recurrent selection allowed a significant 2 to 3 °C increase of the LT50 after four cycles of recurrent selection. Two-dimensional difference gel electrophoresis (2D-DIGE) was used to study variations in protein abundance. Principal component analysis based on 2D-DIGE revealed that the largest variability in the protein data set was attributable to the cold acclimation treatment and that the two genetic backgrounds had differential protein composition in the acclimated state only. Vegetative storage proteins (VSP), which are essential nitrogen reserves for plant regrowth, and dehydrins were among the most striking changes in proteome composition of cold acclimated crowns of red clovers. A subset of proteins varied in abundance in response to selection including a dehydrin that increased in abundance in TF3 and TF4 populations as compared to TF0 in the Endure background.ConclusionRecurrent selection performed indoor is an effective approach to improve the freezing tolerance of red clover. Significant improvement of freezing tolerance by recurrent selection was associated with differential accumulation of a small number of cold-regulated proteins that may play an important role in the determination of the level of freezing tolerance.