The SERK1 protein complexes

Cell fate in plant cells is highly flexible and even differentiated cells can change fate back to the totipotent state. In this study we show that plant steroid hormones are required for this cell fate change. Brassinosteroids are perceived by receptors of the BRI1 and SERK type present in the plasma membrane of plant cells. SERK1 phosphorilation status in vivo is enhanced by brassinosteroid perception and in vitro SERK1 appears to be the most active kinase compared with the other members of the family. Using a combination of biochemical, molecular and cell biological tools the work presented in this thesis shows that the BRI1 and SERK1 receptors transduce the signal from the membrane directly to the nucleus via a transcription factor, AGL15. This is a novel finding in plants where it was not shown that such short signaling transduction pathways are operational

Transcription factor mediated control of anthocyanin biosynthesis in vegetative tissues

Plants accumulate secondary metabolites to adapt to environmental conditions. These compounds, here exemplified by the purple-colored anthocyanins, are accumulated upon high temperatures, UV-light, drought, and nutrient deficiencies, and may contribute to tolerance to these stresses. Producing compounds is often part of a more broad response of the plant to changes in the environment. Here we investigate how a transcription-factor-mediated program for controlling anthocyanin biosynthesis also has effects on formation of specialized cell structures and changes in the plant root architecture. A systems biology approach was developed in tomato (Solanum lycopersicum) for coordinated induction of biosynthesis of anthocyanins, in a tissue- and development-independent manner. A transcription factor couple from Antirrhinum that is known to control anthocyanin biosynthesis was introduced in tomato under control of a dexamethasone-inducible promoter. By application of dexamethasone, anthocyanin formation was induced within 24 h in vegetative tissues and in undifferentiated cells. Profiles of metabolites and gene expression were analyzed in several tomato tissues. Changes in concentration of anthocyanins and other phenolic compounds were observed in all tested tissues, accompanied by induction of the biosynthetic pathways leading from Glc to anthocyanins. A number of pathways that are not known to be involved in anthocyanin biosynthesis were observed to be regulated. Anthocyanin-producing plants displayed profound physiological and architectural changes, depending on the tissue, including root branching, root epithelial cell morphology, seed germination, and leaf conductance. The inducible anthocyanin-production system reveals a range of phenomena that accompanies anthocyanin biosynthesis in tomato, including adaptions of the plants architecture and physiology

Advances in Understanding Brassinosteriod Signaling

Brassinosteroids (BRs) function as signaling molecules in plants and are involved in processes such as stem elongation, vascular differentiation, male fertility, timing of senescence and flowering, leaf development, and resistance to biotic and abiotic stresses. Unlike animal steroids that are perceived by nuclear receptors, BRs are perceived by transmembrane receptor kinase complexes that initiate a phosphorylation-mediated signaling cascade to transduce the steroid signal. BR binding to the extracellular domain of the receptor BRI1 induces kinase activation and hetero-oligomerization with the second transmembrane kinase BAK1. Activated BRI1 then dissociates from the BRI1-interacting protein BKI1, a newly identified negative regulator of BR signaling. In the presence of BR, the kinase BIN2, which is the Arabidopsis homolog of GSK3 (glycogen synthase kinase 3), is inhibited by an unknown mechanism, leading to dephosphorylation of BES1 and BZR1 inside the nucleus. This allows BES1 and BZR1 to homodimerize or combine with other transcription factors to bind to promoters of BR-responsive genes. These studies of BR signaling in plants have revealed signaling pathways that are distinctly different from related ones operating in animal cells

Advances in Understanding Brassinosteriod Signaling

Brassinosteroids (BRs) function as signaling molecules in plants and are involved in processes such as stem elongation, vascular differentiation, male fertility, timing of senescence and flowering, leaf development, and resistance to biotic and abiotic stresses. Unlike animal steroids that are perceived by nuclear receptors, BRs are perceived by transmembrane receptor kinase complexes that initiate a phosphorylation-mediated signaling cascade to transduce the steroid signal. BR binding to the extracellular domain of the receptor BRI1 induces kinase activation and hetero-oligomerization with the second transmembrane kinase BAK1. Activated BRI1 then dissociates from the BRI1-interacting protein BKI1, a newly identified negative regulator of BR signaling. In the presence of BR, the kinase BIN2, which is the Arabidopsis homolog of GSK3 (glycogen synthase kinase 3), is inhibited by an unknown mechanism, leading to dephosphorylation of BES1 and BZR1 inside the nucleus. This allows BES1 and BZR1 to homodimerize or combine with other transcription factors to bind to promoters of BR-responsive genes. These studies of BR signaling in plants have revealed signaling pathways that are distinctly different from related ones operating in animal cells

Comparison of gene expression between wild type and FUL1/2 knockdown tomato fruits

We compared gene expression by microarray analysis between wild type and transgenic sibling progeny from two primary transgenic lines containing a construct for knocking down expression of both tomato fruitfull orthologs, FUL1/TDR4 and FUL2/MBP7

Identification of microRNA targets in tomato fruit development using high-throughput sequencing and degradome analysis

By using parallel analysis of RNA ends (PARE) for global identification of miRNA targets and comparing four different stages of tomato fruit development we identified a large number of target genes of miRNAs. PARE libraries were produced, one each, for tomato fruits at 5 days after pollination, mature green fruit, Breaker fruit, and 7 days after Breaker stge fruit

Proteomics insights into plant signaling and development.

Mass spectrometry-based proteomics is used to gain insight into the abundance and subcellular localization of cellular signaling components, the composition of molecular complexes and the regulation of signaling pathways. Multicellular organisms have evolved signaling networks and fast responses to stimuli that can be discovered and monitored by the use of advanced proteomics techniques in combination with traditional functional analysis. Plants are multicellular organisms and products of tightly regulated developmental programmes that respond to environmental conditions and internal cues. Plant development is orchestrated by inter- and intracellular signaling molecules, receptors and transcriptional regulators, which act in a temporal and spatially coordinated manner. Here we review recent advances in proteomics applications used to understand complex cellular signaling processes in plants

The application of a biostimulant based on tannins afects root architecture and improves tolerance to salinity in tomato plants

Roots have important roles for plants to withstand adverse environmental conditions, including salt stress. Biostimulant application was shown to enhance plant resilience towards abiotic stresses. Here, we studied the effect of a tannin-based biostimulant on tomato (Solanum lycopersicum L.) grown under salt stress conditions. We investigated the related changes at both root architecture (via imaging and biometric analysis) and gene expression (RNA-Seq/qPCR) levels. Moreover, in order to identify the main compounds potentially involved in the observed effects, the chemical composition of the biostimulant was evaluated by UV/Vis and HPLC-ESI-Orbitrap analysis. Sixteen compounds, known to be involved in root development and having a potential antioxidant properties were identified. Significant increase of root weight (+ 24%) and length (+ 23%) was observed when the plants were grown under salt stress and treated with the biostimulant. Moreover, transcriptome analysis revealed that the application of the biostimulant upregulated 285 genes, most of which correlated to root development and salt stress tolerance. The 171 downregulated genes were mainly involved in nutrient uptake. These data demonstrated that the biostimulant is able not only to restore root growth in salty soils, but also to provide the adequate plant nourishment by regulating the expression of essential transcription factors and stress responsive genes

Bacillus thuringiensis delta-endotoxin Cry1Ac domain III enhances activity against Heliothis virescens in some, but not all Cry1-Cry1Ac hybrids

We investigated the role of domain III of Bacillus thuringiensis d-endotoxin Cry1Ac in determining toxicity against Heliothis virescens. Hybrid toxins, containing domain III of Cry1Ac with domains I and II of Cry1Ba, Cry1Ca, Cry1Da, Cry1Ea, and Cry1Fb, respectively, were created. In this way Cry1Ca, Cry1Fb, and to a lesser extent Cry1Ba were made considerably more toxic

Transcriptional control of fleshy fruit development and ripening

Fleshy fruits have evolved to be attractive to frugivores in order to enhance seed dispersal, and have become an indispensable part of the human diet. Here we review the recent advances in the understanding of transcriptional regulation of fleshy fruit development and ripening with a focus on tomato. While aspects of fruit development are probably conserved throughout the angiosperms, including the model plant Arabidopsis thaliana, it is shown that the likely orthologues of Arabidopsis genes have distinct functions in fleshy fruits. The model for the study of fleshy fruit development is tomato, because of the availability of single gene mutants and transgenic knock-down lines. In other species, our knowledge is often incomplete or absent. Tomato fruit size and shape are co-determined by transcription factors acting during formation of the ovary. Other transcription factors play a role in fruit chloroplast formation, and upon ripening impact quality aspects such as secondary metabolite content. In tomato, the transcription factors NON-RIPENING (NOR), COLORLESS NON-RIPENING (CNR), and RIPENING INHIBITOR (MADS-RIN) in concert with ethylene signalling regulate ripening, possibly in response to a developmental switch. Additional components include TOMATO AGAMOUS-LIKE1 (TAGL1), APETALA2a (AP2a), and FRUITFULL (FUL1 and FUL2). The links between this highly connected regulatory network and downstream effectors modulating colour, texture, and flavour are still relatively poorly understood. Intertwined with this network is post-transcriptional regulation by fruit-expressed micro-RNAs targeting several of these transcription factors. This important developmental process is also governed by changes in DNA methylation levels and possibly chromatin remodelling