An ortholog of the MADS-box gene SEPALLATA3 regulates stamen development in the woody plant Jatropha curcas.

MAIN CONCLUSION: Overexpression of JcSEP3 causes defective stamen development in Jatropha curcas, in which brassinosteroid and gibberellin signaling pathways may be involved. SEPALLATAs (SEPs), the class E genes of the ABCE model, are required for floral organ determination. In this study, we investigated the role of the JcSEP3 gene in floral organ development in the woody plant Jatropha curcas. Transgenic Jatropha plants overexpressing JcSEP3 displayed abnormal phenotypes such as deficient anthers and pollen, as well as free stamen filaments, whereas JcSEP3-RNA interference (RNAi) transgenic plants had no obvious phenotypic changes, suggesting that JcSEP3 is redundant with other JcSEP genes in Jatropha. Moreover, we compared the transcriptomes of wild-type plants, JcSEP3-overexpressing, and JcSEP3-RNAi transgenic plants. In the JcSEP3-overexpressing transgenic plants, we discovered 25 upregulated genes involved in anther and pollen development, as well as 12 induced genes in brassinosteroid (BR) and gibberellin (GA) signaling pathways. These results suggest that JcSEP3 directly or indirectly regulates stamen development, concomitant with the regulation of BR and GA signaling pathways. Our findings help to understand the roles of SEP genes in stamen development in perennial woody plants.

Arabidopsis CURLY LEAF functions in leaf immunity against fungal pathogens by concomitantly repressing SEPALLATA3 and activating ORA59.

Arabidopsis non-host resistance against non-adapted fungal pathogens including Colletotrichum fungi consists of pre-invasive and post-invasive immune responses. Here we report that non-host resistance against non-adapted Colletotrichum spp. in Arabidopsis leaves requires CURLY LEAF (CLF), which is critical for leaf development, flowering and growth. Microscopic analysis of pathogen behavior revealed a requirement for CLF in both pre- and post-invasive non-host resistance. The loss of a functional SEPALLATA3 (SEP3) gene, ectopically expressed in clf mutant leaves, suppressed not only the defect of the clf plants in growth and leaf development but also a defect in non-host resistance against the non-adapted Colletotrichum tropicale. However, the ectopic overexpression of SEP3 in Arabidopsis wild-type leaves did not disrupt the non-host resistance. The expression of multiple plant defensin (PDF) genes that are involved in non-host resistance against C. tropicale was repressed in clf leaves. Moreover, the Octadecanoid-responsive Arabidopsis 59 (ORA59) gene, which is required for PDF expression, was also repressed in clf leaves. Notably, when SEP3 was overexpressed in the ora59 mutant background, C. tropicale produced clear lesions in the inoculated leaves, indicating an impairment in non-host resistance. Furthermore, ora59 plants overexpressing SEP3 exhibited a defect in leaf immunity to the adapted Colletotrichum higginsianum. Since the ora59 plants overexpressing SEP3 did not display obvious leaf curling or reduced growth, in contrast to the clf mutants, these results strongly suggest that concomitant SEP3 repression and ORA59 induction via CLF are required for Arabidopsis leaf immunity to Colletotrichum fungi, uncoupled from CLF's function in growth and leaf development.

First proteome study of sporadic flowering in bamboo species (Bambusa vulgaris and Dendrocalamus manipureanus) reveal the boom is associated with stress and mobile genetic elements.

Bamboo species are the fastest-growing plants having a long vegetative cycle. Abrupt switching from the vegetative phase to the reproductive phase via sporadic flowering boom, occasionally leads to death of bamboo clumps, and threatens the existence of many bamboo species. To apprehend the molecular mechanism driving sporadic flowering, proteome changes in the initial and advanced floral buds of two edible bamboo species (Bambusa vulgaris and Dendrocalamus manipureanus) was dissected by two-dimensional gel electrophoresis (2-DE). A total of 39 differentially expressed peptide spots were identified by matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF-TOF/MS). In both B. vulgaris and D. manipureanus, identified proteins were categorized as transposon-related, defence and stress-related, cell cycle related, metabolism related, signal transduction related, and some lacked known putative domains. Proteins such as SEPALLATA3, ubiquitin, histone 3, thaumatin-like protein, putative tethering factor, SF-assemblin, polyubiquitin, mitochondrial carrier-like protein and RPT2-like protein were significantly expressed. Differences in D. manipureanus and B. vulgaris suggested that bamboo species have diverse 'drivers' or 'passengers' genes that govern natural sporadic flowering boom. This first floral proteomics analysis of bamboos revealed that sporadic boom is a highly energetic process, associated with stress elements, mobile genetic elements and signal transduction cross-talk elements.

Imaging early stages of the female reproductive structure of Arabidopsis by confocal laser scanning microscopy.

BACKGROUND: The gynoecium is the female reproductive structure and probably the most complex plant structure. During its development, different internal tissues and structures are formed. Insights in gene expression or hormone localization patterns are key to understanding gynoecium development from a molecular biology point of view. RESULTS: Imaging with a confocal laser scanning microscope (CLSM) is a widely used strategy; however, visualization of internal developmental expression patterns in the Arabidopsis gynoecium can be technically challenging. Here, we present a detailed protocol that allows the visualization of internal expression patterns at high resolution during gynoecium development. We demonstrate the applicability using a cytokinin response marker (TCS::GFP), an auxin response marker (DR5::VENUS), and a SEPALLATA3 marker (SEP3::SEP3:GFP). CONCLUSIONS: The detailed protocol presented here allows the visualization of fluorescence signals in internal structures during Arabidopsis gynoecium development. This protocol may also be adapted for imaging other challenging plant structures or organs.

Evolution of the Plant Reproduction Master Regulators LFY and the MADS Transcription Factors: The Role of Protein Structure in the Evolutionary Development of the Flower.

Understanding the evolutionary leap from non-flowering (gymnosperms) to flowering (angiosperms) plants and the origin and vast diversification of the floral form has been one of the focuses of plant evolutionary developmental biology. The evolving diversity and increasing complexity of organisms is often due to relatively small changes in genes that direct development. These "developmental control genes" and the transcription factors (TFs) they encode, are at the origin of most morphological changes. TFs such as LEAFY (LFY) and the MADS-domain TFs act as central regulators in key developmental processes of plant reproduction including the floral transition in angiosperms and the specification of the male and female organs in both gymnosperms and angiosperms. In addition to advances in genome wide profiling and forward and reverse genetic screening, structural techniques are becoming important tools in unraveling TF function by providing atomic and molecular level information that was lacking in purely genetic approaches. Here, we summarize previous structural work and present additional biophysical and biochemical studies of the key master regulators of plant reproduction - LEAFY and the MADS-domain TFs SEPALLATA3 and AGAMOUS. We discuss the impact of structural biology on our understanding of the complex evolutionary process leading to the development of the bisexual flower.

Crystallization studies of the keratin-like domain from Arabidopsis thaliana SEPALLATA 3.

In higher plants, the MADS-box genes encode a large family of transcription factors (TFs) involved in key developmental processes, most notably plant reproduction, flowering and floral organ development. SEPALLATA 3 (SEP3) is a member of the MADS TF family and plays a role in the development of the floral organs through the formation of multiprotein complexes with other MADS-family TFs. SEP3 is divided into four domains: the M (MADS) domain, involved in DNA binding and dimerization, the I (intervening) domain, a short domain involved in dimerization, the K (keratin-like) domain important for multimeric MADS complex formation and the C (C-terminal) domain, a largely unstructured region putatively important for higher-order complex formation. The entire K domain along with a portion of the I and C domains of SEP3 was crystallized using high-throughput robotic screening followed by optimization. The crystals belonged to space group P2(1)2(1)2, with unit-cell parameters a = 123.44, b = 143.07, c = 49.83 Å, and a complete data set was collected to 2.53 Šresolution.