Tissue specific action of Gibberellin in Arabidopsis flowering and development

This work focuses on understanding the roles of the plant hormone gibberellin (GA) in controlling the initiation of flowering in Arabidopsis thaliana. GA is essential to promote the transition to flowering under non inductive short-­‐day (SD) photoperiods by activating transcription of the floral integrator SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and of the meristem identity gene LEAFY (LFY). However, mutations in GA receptors also prevent flowering under inductive long days (LDs), suggesting that this hormone also has crucial functions in the initiation of flowering under these conditions. Here by overexpressing the GA catabolic enzyme GIBBERELLIN 2 OXIDASE 7 (GA2ox7) in specific plant organs, we show that GAs play important regulatory roles in the leaves and shoot apical meristem (SAM) to promote flowering under LDs. Our results suggest that GAs are required in the leaf to increase levels of FT mRNA, which encodes a protein that is part of the systemic florigen signal of Arabidopsis. At the SAM GAs promote expression of SQUAMOSA PROMOTER BINDING PROMOTER LIKE (SPL) genes downstream of the floral integrator SOC1. In addition, we characterised a novel function of the MADS box transcription factor SHORT VEGETATIVE PHASE (SVP) and demonstrated its link to the GA biosynthetic pathway at the SAM. Mutation of SVP results in a significant accumulation of active GA4 through the upregulation of GIBBERELLIN 20-­‐OXIDASE 2 (GA20ox2), which encodes an enzyme involved in GA biosynthesis. Conversely overexpression of SVP from the 35S promoter causes phenotypes characteristic of GA deficiency plants. We demonstrate that the SVP/GA20ox2 module is controlled by photoperiod through FT, TSF and SOC1 at the SAM. Wild-­‐type plants shifted from SDs to LDs showed downregulation of SVP in the centre of the SAM and increased levels of GA20ox2 transcripts in the rib meristem region. These expression patterns are significantly compromised in plants lacking FT, TSF or SOC1 functions. We propose that in response to LDs, FT, TSF and SOC1 act to repress expression of SVP leading to upregulation of GA20ox2. The activation of GA20ox2 expression causes increased GA content, which promotes flowering by activating transcription of SPL genes. Finally, we identified a link between a core subunit of chromatin remodelling complexes (CRCs) SWI3C and the GA signalling and biosynthesis pathways. The swi3c mutant displayed several developmental impairments, which resembled those of GA deficient plants. In agreement with the phenotypic characterization, swi3c mutants showed lower levels of active GAs and reduced mRNA abundance of the GA receptor GIDa, suggesting that SWI3C is required to control development by modulating GA biosynthesis and perception. Moreover we demonstrate that SWI3C binds in vivo to some of the DELLA repressors (RGA, RGL1, RGL2, RGL3) and SPY O-­‐GlcNAc transferase, two components of the GA signalling pathway. Our results indicate that CRCs control plant development at least in part by promoting GA biosynthesis, and by regulating expression of some GA responsive genes. Overall this work increases our understanding of the regulation of GA biosynthesis and signalling, as well as demonstrating new functions for these processes in the control of the floral transition

Utilizzo di metodologie genetico-molecolari nell'identificazione di nuovi geni regolatori di GIGANTEA in Arabidopsis thaliana

Negli organismi e in particolare nel regno vegetale, l’orologio biologico o “circadian clock” ha la funzione di regolare molti dei processi fisiologici e metabolici. Diversi geni e proteine che partecipano alla regolazione del clock sono stati identificati per lo più attraverso l’uso della biologia molecolare. Tuttavia, le scoperte fatte fino a questo momento non sono sufficienti per spiegare e comprendere a fondo la complessità dei meccanismi del clock, indicando che molti dei suoi regolatori sono ancora a noi sconosciuti. Dati sperimentali e modelli matematici suggeriscono fortemente che il gene GIGANTEA (GI) può essere uno di questi regolatori; in mutanti gi si osserva l’alterazione delle altre componenti chiave dell’orologio. GI è anche coinvolto in altri processi fisiologici di notevole importanza come l’induzione fotoperiodica e la risposta alla luce rossa e blu, suggerendo un importante ruolo di questo gene nei processi di sviluppo delle piante. Malgrado l’importanza di GI in tali processi, la sua funzione biochimica e la sua regolazione a livello molecolare sono aspetti ancora da chiarire. Il principale obiettivo di questo progetto è quello di incrementare le conoscenze attuali sul funzionamento del clock e, più nello specifico, di comprendere i meccanismi alla base della regolazione di GIGANTEA. Il trascritto del gene è regolato dal circadian clock ed è caratterizzato da un picco di espressione durante il pomeriggio. Il progetto è stato dedicato maggiormente all’identificazione di nuovi geni o alleli, che ritardano o anticipano il picco di espressione di GI (GI timing). Questi sono identificati con lo studio delle variazioni genetico-naturali, effettuato attraverso il QTL mapping e fine mapping di differenti accessioni di Arabidopsis thaliana. Per perseguire tali obiettivi, il promotore di GIGANTEA è stato fuso col gene della luciferasi, ottenendo così un gene reporter che permette di monitorarne l’espressione, andando così a definire un preciso GI timing; diversi ecotipi di Arabidopsis sono stati trasformati con questo costrutto e il picco di espressione del gene è stato assunto come tratto fenotipico. Diverse accessioni di Arabidopsis mostrano differenti GI timing e le stesse sono state incrociate, al fine di generare delle popolazioni (mapping population) utilizzate per mappare i QTL (Quantitative Trait Loci) che regolano il tratto fenotipico. Nel caso specifico sono state studiate tre accessioni: Columbia, Dijon G e Lip 0, che mostrano differenti fenotipi; Columbia ha un GI timing anticipato di circa un’ora e mezzo (early phenotype) rispetto a quello di Dijon G e Lip 0 (late phenotype). Il QTL mapping effettuato sulla F2 population di Columbia X Lip 0 cross e Columbia X Dijon G cross ha evidenziato la presenza di numerosi QTL responsabili della regolazione del GI timing. Il fine mapping di alcuni di questi QTL ha suggerito che il gene PHYB (fitocromo B) è uno dei regolatori di GIGANTEA. Gli studi effettuati sull’espressione dei geni appartenenti all’orologio biologico hanno invece messo in evidenza che un’altra componente genica del clock, di nome CCA1, è in stretta relazione con GI ed è caratterizzata da differenti timing nei tre ecotipi studiat

Recovery and sanitary selection of local vines of the Sardinia

A study was made on the recovery genotypes local grapevine with the aim to conserve them and to evaluate their health status and thus to improve the quality of the propagation material. Clone accessions of 61 vines were grafted and placed in a germoplasma field. The varieties that were considered enologically valuable were subjected to sanitary selection. Some vines showed indubitable healthy qualities, and should be immediately evaluated from an economical point view and then certificated. Possible sanitation treatments were also evaluated, with the aim of extending the number clone accessions to be included in experimental trials to access their yield

Carrier assisted dyeing of m-aramid fibers

The excellence in quality of Biella wool fabric, provided from the last 40 years one of first position in all over the world for the “Biella textile district”. In the last decade competition of developing countries became ruthless regarding the common textile like wool for a lot of reason, first of all cheaper labor. Industries started to move production over there but, fortunately, the know-how has remained here. For these reasons, since the past 10 years the world of textile, especially in Europe and USA, is moving to another kind of textile and garments dimension: the Technical Textile. Aramids are, since 90’s, the most important technical textile for protection garments, and in Biella district a lot of factories started to handle them. Since some factories started to produce yarn and fabric for protective garments, the need to dye them has come. The market nowadays requires, even for protective goods, not only the conventional coloration with which the fiber is produced in large scale by manufacturers, but all the typical color ranges of other common textile fibers. Nomex® fiber is probably the most important m-aramid used for this scope and its dyeing recipes are well known. However, Nomex® is not easily available for factories due to particular commercial agreements, and is very expensive. Other branded m-aramid fibers exist on the market having same technical properties of Nomex® but, unfortunately, not exactly the same dyeability. In 2010 a regional research project called FILIDEA was born between Politecnico di Torino and Marchi&Fildi Company. One of the 6 research working packages was thought to overcome the difficulties in dyeing a m-aramid fiber called X-Fiper® and produced by a Chinese company called SRO. From this project, since the important results obtained in the first two years of research work, a Ph.D. project was born in 2012. Therefore, the aim of this Ph.D. project is to investigate the dyeing process of this particular fiber starting from the examination of its properties