Strigolactones (SLs), a class of the most recently identified terpenoid phytohormones, play essential roles in plant development, specifically in suppressing shoot branching. MAX2, a subunit of an SCF E3 ligase and a positive regulator that inhibits shoot branching, is likely a key SL signaling component. Here, we provide genetic and biochemical evidence to demonstrate that BES1 interacts with MAX2 and acts as its substrate to regulate SL-responsive gene expression. Additional AtD14, a putative receptor of SLs, can promote BES1 degradation. Knockdown of BES1 and its homologs dramatically suppressed the branching phenotype of max2-1 mutant. These results portray an SL signaling cascade from the putative receptor to downstream transcription factors. In addition, we demonstrate that the SL and brassinosteroid (BR) signaling pathways distinctly regulate the same transcription factor, BES1, to control specific developmental processes.

The development of anther and pollen is important for male reproduction, and this process is coordinately regulated by many external and internal cues. In this study, we systematically examined the male reproductive phenotypes of a series of brassinosteroid biosynthetic and signaling mutants and found that, besides the expected cell-expansion defects, these mutants also showed reduced pollen number, viability, and release efficiency. These defects were related with abnormal tapetum and microspore development. Using both real-time quantitative RT-PCR and microarray experiments, we found that the expression of many key genes required for anther and pollen development was suppressed in these mutants. ChIP analysis demonstrated that BES1, an important transcription factor for brassinosteroid signaling, could directly bind to the promoter regions of genes encoding transcription factors essential for anther and pollen development, SPL/NZZ, TDF1, AMS, MS1, and MS2. Taken together, these data lead us to propose that brassinosteroids control male fertility at least in part via directly regulating key genes for anther and pollen development in Arabidopsis. Our work provides a unique mechanism to explain how a phytohormone regulates an essential genetic program for plant development.male fertility | regulatory network | signaling | chromatin immunoprecipitation

In Arabidopsis, root hair and non-hair cell fates are determined by a MYB-bHLH-WD40 transcriptional complex and are regulated by many internal and environmental cues. Brassinosteroids play important roles in regulating root hair specification by unknown mechanisms. Here, we systematically examined root hair phenotypes in brassinosteroid-related mutants, and found that brassinosteroid signaling inhibits root hair formation through GSK3-like kinases or upstream components. We found that with enhanced brassinosteroid signaling, GL2, a cell fate marker for non-hair cells, is ectopically expressed in hair cells, while its expression in non-hair cells is suppressed when brassinosteroid signaling is reduced. Genetic analysis demonstrated that brassinosteroid-regulated root epidermal cell patterning is dependent on the WER-GL3/EGL3-TTG1 transcriptional complex. One of the GSK3-like kinases, BIN2, interacted with and phosphorylated EGL3, and EGL3s mutated at phosphorylation sites were retained in hair cell nuclei. BIN2 phosphorylated TTG1 to inhibit the activity of the WER-GL3/EGL3-TTG1 complex. Thus, our study provides insights into the mechanism of brassinosteroid regulation of root hair patterning.DOI: http://dx.doi.org/10.7554/eLife.02525.001

Myasthenia gravis (MG) is a chronic humoral immunity-mediated autoimmune disorder of the neuromuscular junction characterized by muscle weakness. Follicular helper T (Tfh) cells may be the key Th cell subset that promotes MG development, as their major function is helping B cell activation and Ab production. Aberrance of thymus-derived Tfh cells might be implicated in autoimmune diseases including MG; just how circulating Tfh cells, especially those from patients with a normal thymus, contribute to MG pathogenesis remains to be uncovered. In this article, we characterize a population of circulating CD4(+)CXCR5(+)PD-1(+) Tfh cells in ocular and generalized MG patients without thymic abnormalities and demonstrate that the circulating Tfh cells are significantly enriched in generalized MG patients but not in ocular MG patients compared with healthy subjects, whereas a proportion of follicular regulatory T cells decreased in MG patients. In addition, the frequency of plasma cells and B cells was higher and the serum levels of IL-6/IL-21 were also elevated in these MG patients. The activated Tfh1 and Tfh17 in Tfh cells are the major source for IL-21 production in MG patients. A strong correlation between Tfh cells and the plasma cell frequency and anti-acetylcholine receptor Ab titers was evident in generalized MG patients. In particular, we found that Tfh cells derived from MG patients promoted B cells to produce Abs in an IL-21 signaling-dependent manner. Collectively, our results suggest that circulating Tfh cells may act on autoreactive B cells and thus contribute to the development of MG in patients without thymic abnormalities.

Verticillium wilt of potato is caused by the fungus pathogen Verticillium dahliae. Present sRNA sequencing data revealed that miR482 was in response to V. dahliae infection, but the function in potato is elusive. Here, we characterized potato miR482 family and its putative role resistance to Verticillium wilt. Members of the potato miR482 superfamily are variable in sequence, but all variants target a class of disease-resistance proteins with nucleotide binding site (NBS) and leucine-rich repeat (LRR) motifs. When potato plantlets were infected with V. dahliae, the expression level of miR482e was downregulated, and that of several NBS-LRR targets of miR482e were upregulated. Transgenic potato plantlets overexpressing miR482e showed hypersensitivity to V. dahliae infection. Using sRNA and degradome datasets, we validated that miR482e targets mRNAs of NBS-LRR disease-resistance proteins and triggers the production of trans-acting (ta)-siRNAs, most of which target mRNAs of defense-related proteins. Thus, the hypersensitivity of transgenic potato could be explained by enhanced miR482e and miR482e-derived tasiRNA-mediated silencing on NBS-LRR-disease-resistance proteins. It is speculated that a miR482-mediated silencing cascade mechanism is involved in regulating potato resistance against V. dahliae infection and could be a counter defense action of plant in response to pathogen infection.Keywords: miR482; nucleotide binding site leucine-rich repeat; potato; sRNA; ta-siRNA; Verticillium dahliae; Verticillium wilt Citation: Yang L, Mu X, Liu C, Cai J, Shi K, Zhu W, Yang Q (2015) Overexpression of potato miR482e enhanced plant sensitivity to Verticillium dahliae infection.

Heat shock transcription factors (Hsfs) play vital roles in the regulation of tolerance to various stresses in living organisms. To dissect the mechanisms of the Hsfs in potato adaptation to abiotic stresses, genome and transcriptome analyses of Hsf gene family were investigated in Solanum tuberosum L. Twenty-seven StHsf members were identified by bioinformatics and phylogenetic analyses and were classified into A, B, and C groups according to their structural and phylogenetic features. StHsfs in the same class shared similar gene structures and conserved motifs. The chromosomal location analysis showed that 27 Hsfs were located in 10 of 12 chromosomes (except chromosome 1 and chromosome 5) and that 18 of these genes formed 9 paralogous pairs. Expression profiles of StHsfs in 12 different organs and tissues uncovered distinct spatial expression patterns of these genes and their potential roles in the process of growth and development. Promoter and quantitative real-time polymerase chain reaction (qRT-PCR) detections of StHsfs were conducted and demonstrated that these genes were all responsive to various stresses. StHsf004, StHsf007, StHsf009, StHsf014, and StHsf019 were constitutively expressed under non-stress conditions, and some specific Hsfs became the predominant Hsfs in response to different abiotic stresses, indicating their important and diverse regulatory roles in adverse conditions. A co-expression network between StHsfs and StHsf -co-expressed genes was generated based on the publicly-available potato transcriptomic databases and identified key candidate StHsfs for further functional studies.

The natural polyamine spermidine and spermine have been reported to ameliorate aging and aging-induced dementia. However, the mechanism is still confused. An aging model, the senescence accelerated mouse-8 (SAMP8), was used in this study. Novel object recognition and the open field test results showed that oral administration of spermidine, spermine and rapamycin increased discrimination index, modified number, inner squares distance and times. Spermidine and spermine increased the activity of SOD, and decreased the level of MDA in the aging brain. Spermidine and spermine phosphorylate AMPK and regulate autophagy proteins (LC3, Beclin 1 and p62). Spermidine and spermine balanced mitochondrial and maintain energy for neuron, with the regulation of MFN1, MFN2, DRP1, COX IV and ATP. In addition, western blot results (Bcl-2, Bax and Caspase-3, NLRP3, IL-18, IL-1β) showed that spermidine and spermine prevented apoptosis and inflammation, and elevate the expression of neurotrophic factors, including NGF, PSD95and PSD93 and BDNF in neurons of SAMP8 mice. These results indicated that the effect of spermidine and spermine on anti-aging is related with improving autophagy and mitochondrial function.

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