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Dive into the research topics where Alessandro Alboresi is active.

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Featured researches published by Alessandro Alboresi.


Plant Journal | 2008

MYBL2 is a new regulator of flavonoid biosynthesis in Arabidopsis thaliana

Christian Dubos; Jose-Sabrina Le Gourrierec; Antoine Baudry; Gunnar Huep; Elodie Lanet; Isabelle Debeaujon; Jean-Marc Routaboul; Alessandro Alboresi; Bernd Weisshaar; Loïc Lepiniec

SUMMARY In Arabidopsis thaliana, several MYB and basic helix-loop-helix (BHLH) proteins form ternary complexes with TTG1 (WD-Repeats) and regulate the transcription of genes involved in anthocyanin and proanthocyanidin (PA) biosynthesis. Similar MYB-BHLH-WDR (MBW) complexes control epidermal patterning and cell fates. A family of small MYB proteins (R3-MYB) has been shown to play an important role in the regulation of epidermal cell fates, acting as inhibitors of the MBW complexes. However, so far none of these small MYB proteins have been demonstrated to regulate flavonoid biosynthesis. The genetic and molecular analyses presented here demonstrated that Arabidopsis MYBL2, which encodes a R3-MYB-related protein, is involved in the regulation of flavonoid biosynthesis. The loss of MYBL2 activity in the seedlings of two independent T-DNA insertion mutants led to a dramatic increase in the accumulation of anthocyanin. In addition, overexpression of MYBL2 in seeds inhibited the biosynthesis of PAs. These changes in flavonoid content correlate well with the increased level of mRNA of several structural and regulatory anthocyanin biosynthesis genes. Interestingly, transient expression analyses in A. thaliana cells suggested that MYBL2 interacts with MBW complexes in planta and directly modulates the expression of flavonoid target genes. These results are fully consistent with the molecular interaction of MYBL2 with BHLH proteins observed in yeast. Finally, MYBL2 expression studies, including its inhibition by light-induced stress, allowed us to hypothesise a physiological role for MYBL2. Taken together, these results bring new insights into the transcriptional regulation of flavonoid biosynthesis and provide new clues and tools for further investigation of its developmental and environmental regulation.


Proceedings of the National Academy of Sciences of the United States of America | 2010

Physcomitrella patens mutants affected on heat dissipation clarify the evolution of photoprotection mechanisms upon land colonization

Alessandro Alboresi; Caterina Gerotto; Giorgio M. Giacometti; Roberto Bassi; Tomas Morosinotto

Light is the source of energy for photosynthetic organisms; when in excess, however, it also drives the formation of reactive oxygen species and, consequently, photoinhibition. Plants and algae have evolved mechanisms to regulate light harvesting efficiency in response to variable light intensity so as to avoid oxidative damage. Nonphotochemical quenching (NPQ) consists of the rapid dissipation of excess excitation energy as heat. Although widespread among oxygenic photosynthetic organisms, NPQ shows important differences in its machinery. In land plants, such as Arabidopsis thaliana, NPQ depends on the presence of PSBS, whereas in the green alga Chlamydomonas reinhardtii it requires a different protein called LHCSR. In this work, we show that both proteins are present in the moss Physcomitrella patens. By generating KO mutants lacking PSBS and/or LHCSR, we also demonstrate that both gene products are active in NPQ. Plants lacking both proteins are more susceptible to high light stress than WT, implying that they are active in photoprotection. These results suggest that NPQ is a fundamental mechanism for survival in excess light and that upon land colonization, photosynthetic organisms evolved a unique mechanism for excess energy dissipation before losing the ancestral one found in algae.


Plant Physiology | 2008

The Arabidopsis Abscisic Acid Catabolic Gene CYP707A2 Plays a Key Role in Nitrate Control of Seed Dormancy

Theodoros Matakiadis; Alessandro Alboresi; Yusuke Jikumaru; Kiyoshi Tatematsu; Olivier Pichon; Jean-Pierre Renou; Yuji Kamiya; Eiji Nambara; Hoai-Nam Truong

Nitrate releases seed dormancy in Arabidopsis (Arabidopsis thaliana) Columbia accession seeds in part by reducing abscisic acid (ABA) levels. Nitrate led to lower levels of ABA in imbibed seeds when included in the germination medium (exogenous nitrate). Nitrate also reduced ABA levels in dry seeds when provided to the mother plant during seed development (endogenous nitrate). Transcript profiling of imbibed seeds treated with or without nitrate revealed that exogenous nitrate led to a higher expression of nitrate-responsive genes, whereas endogenous nitrate led to a profile similar to that of stratified or after-ripened seeds. Profiling experiments indicated that the expression of the ABA catabolic gene CYP707A2 was regulated by exogenous nitrate. The cyp707a2-1 mutant failed to reduce seed ABA levels in response to both endogenous and exogenous nitrate. In contrast, both endogenous and exogenous nitrate reduced ABA levels of the wild-type and cyp707a1-1 mutant seeds. The CYP707A2 mRNA levels in developing siliques were positively correlated with different nitrate doses applied to the mother plants. This was consistent with a role of the CYP707A2 gene in controlling seed ABA levels in response to endogenous nitrate. The cyp707a2-1 mutant was less sensitive to exogenous nitrate for breaking seed dormancy. Altogether, our data underline the central role of the CYP707A2 gene in the nitrate-mediated control of ABA levels during seed development and germination.


PLOS ONE | 2008

In Silico and Biochemical Analysis of Physcomitrella patens Photosynthetic Antenna: Identification of Subunits which Evolved upon Land Adaptation

Alessandro Alboresi; Stefano Caffarri; Fabien Nogué; Roberto Bassi; Tomas Morosinotto

BACKGROUND In eukaryotes the photosynthetic antenna system is composed of subunits encoded by the light harvesting complex (Lhc) multigene family. These proteins play a key role in photosynthesis and are involved in both light harvesting and photoprotection. The moss Physcomitrella patens is a member of a lineage that diverged from seed plants early after land colonization and therefore by studying this organism, we may gain insight into adaptations to the aerial environment. PRINCIPAL FINDINGS In this study, we characterized the antenna protein multigene family in Physcomitrella patens, by sequence analysis as well as biochemical and functional investigations. Sequence identification and analysis showed that some antenna polypeptides, such as Lhcb3 and Lhcb6, are present only in land organisms, suggesting they play a role in adaptation to the sub-aerial environment. Our functional analysis which showed that photo-protective mechanisms in Physcomitrella patens are very similar to those in seed plants fits with this hypothesis. In particular, Physcomitrella patens also activates Non Photochemical Quenching upon illumination, consistent with the detection of an ortholog of the PsbS protein. As a further adaptation to terrestrial conditions, the content of Photosystem I low energy absorbing chlorophylls also increased, as demonstrated by differences in Lhca3 and Lhca4 polypeptide sequences, in vitro reconstitution experiments and low temperature fluorescence spectra. CONCLUSIONS This study highlights the role of Lhc family members in environmental adaptation and allowed proteins associated with mechanisms of stress resistance to be identified within this large family.


Systematic and Applied Microbiology | 2002

Molecular characterization of ochratoxin A producing strains of the genus Penicillium

G. Castellá; Thomas Ostenfeld Larsen; Javier Cabanes; Holger Schmidt; Alessandro Alboresi; Ludwig Niessen; P. Färber; Rolf Geisen

Sixty-six strains classified as P. verrucosum based on morphological criteria were characterized by molecular methods like RAPD, AFLP and ITS sequencing. Two groups could be identified by RAPD and AFLP analyses. The two RAPD as well as the two AFLP groups were completely coincidental. Strains in the two groups differed in their ability to produce ochratoxin A, with group I containing mainly high producing strains, and group II containing moderate to non-producing strains. The strains from group I originate from foods, such as cheeses and meat products, while the strains from group II originate from plants. The ribosomal ITS1-5.8S-ITS2 sequences were similar, except for two single nucleotide exchanges in several strains of each group. A chemotaxonomical analysis of some of the strains identified differences between the groups in secondary metabolite production. Strains from group I possessed the chemotype of P. nordicum and strains from group II that of P. verrucosum. The differences at the RAPD and AFLP level, which parallel the chemotypic differences, are consistent with the recent reclassification of ochratoxin A producing penicillia to be either P. verrucosum or P. nordicum. The homolgy between the ITS sequences however indicates phylogenetic relationship between the two species.


BMC Plant Biology | 2011

Reactive oxygen species and transcript analysis upon excess light treatment in wild-type Arabidopsis thaliana vs a photosensitive mutant lacking zeaxanthin and lutein

Alessandro Alboresi; Luca Dall'Osto; Alessio Aprile; Petronia Carillo; Enrica Roncaglia; Luigi Cattivelli; Roberto Bassi

BackgroundReactive oxygen species (ROS) are unavoidable by-products of oxygenic photosynthesis, causing progressive oxidative damage and ultimately cell death. Despite their destructive activity they are also signalling molecules, priming the acclimatory response to stress stimuli.ResultsTo investigate this role further, we exposed wild type Arabidopsis thaliana plants and the double mutant npq1lut2 to excess light. The mutant does not produce the xanthophylls lutein and zeaxanthin, whose key roles include ROS scavenging and prevention of ROS synthesis. Biochemical analysis revealed that singlet oxygen (1O2) accumulated to higher levels in the mutant while other ROS were unaffected, allowing to define the transcriptomic signature of the acclimatory response mediated by 1O2 which is enhanced by the lack of these xanthophylls species. The group of genes differentially regulated in npq1lut2 is enriched in sequences encoding chloroplast proteins involved in cell protection against the damaging effect of ROS. Among the early fine-tuned components, are proteins involved in tetrapyrrole biosynthesis, chlorophyll catabolism, protein import, folding and turnover, synthesis and membrane insertion of photosynthetic subunits. Up to now, the flu mutant was the only biological system adopted to define the regulation of gene expression by 1O2. In this work, we propose the use of mutants accumulating 1O2 by mechanisms different from those activated in flu to better identify ROS signalling.ConclusionsWe propose that the lack of zeaxanthin and lutein leads to 1O2 accumulation and this represents a signalling pathway in the early stages of stress acclimation, beside the response to ADP/ATP ratio and to the redox state of both plastoquinone pool. Chloroplasts respond to 1O2 accumulation by undergoing a significant change in composition and function towards a fast acclimatory response. The physiological implications of this signalling specificity are discussed.


The Plant Cell | 2013

Zeaxanthin Binds to Light-Harvesting Complex Stress-Related Protein to Enhance Nonphotochemical Quenching in Physcomitrella patens

Alberta Pinnola; Luca Dall’Osto; Caterina Gerotto; Tomas Morosinotto; Roberto Bassi; Alessandro Alboresi

In the moss Physcomitrella patens, LHCSR and PSBS, which trigger nonphotochemical quenching (NPQ) in green algae and vascular plants, respectively, are both active. This work reports that zeaxanthin, an NPQ enhancer, is far more active on LHCSR-dependent NPQ than on the PSBS-dependent NPQ. Consistent with this, zeaxanthin binds LHCSR in excess light. Nonphotochemical quenching (NPQ) dissipates excess energy to protect the photosynthetic apparatus from excess light. The moss Physcomitrella patens exhibits strong NPQ by both algal-type light-harvesting complex stress-related (LHCSR)–dependent and plant-type S subunit of Photosystem II (PSBS)-dependent mechanisms. In this work, we studied the dependence of NPQ reactions on zeaxanthin, which is synthesized under light stress by violaxanthin deepoxidase (VDE) from preexisting violaxanthin. We produced vde knockout (KO) plants and showed they underwent a dramatic reduction in thermal dissipation ability and enhanced photoinhibition in excess light conditions. Multiple mutants (vde lhcsr KO and vde psbs KO) showed that zeaxanthin had a major influence on LHCSR-dependent NPQ, in contrast with previous reports in Chlamydomonas reinhardtii. The PSBS-dependent component of quenching was less dependent on zeaxanthin, despite the near-complete violaxanthin to zeaxanthin exchange in LHC proteins. Consistent with this, we provide biochemical evidence that native LHCSR protein binds zeaxanthin upon excess light stress. These findings suggest that zeaxanthin played an important role in the adaptation of modern plants to the enhanced levels of oxygen and excess light intensity of land environments.


BMC Plant Biology | 2009

Antenna complexes protect Photosystem I from Photoinhibition

Alessandro Alboresi; Matteo Ballottari; Rainer Hienerwadel; Giorgio M. Giacometti; Tomas Morosinotto

BackgroundPhotosystems are composed of two moieties, a reaction center and a peripheral antenna system. In photosynthetic eukaryotes the latter system is composed of proteins belonging to Lhc family. An increasing set of evidences demonstrated how these polypeptides play a relevant physiological function in both light harvesting and photoprotection. Despite the sequence similarity between antenna proteins associated with the two Photosystems, present knowledge on their physiological role is mostly limited to complexes associated to Photosystem II.ResultsIn this work we analyzed the physiological role of Photosystem I antenna system in Arabidopsis thaliana both in vivo and in vitro. Plants depleted in individual antenna polypeptides showed a reduced capacity for photoprotection and an increased production of reactive oxygen species upon high light exposure. In vitro experiments on isolated complexes confirmed that depletion of antenna proteins reduced the resistance of isolated Photosystem I particles to high light and that the antenna is effective in photoprotection only upon the interaction with the core complex.ConclusionWe show that antenna proteins play a dual role in Arabidopsis thaliana Photosystem I photoprotection: first, a Photosystem I with an intact antenna system is more resistant to high light because of a reduced production of reactive oxygen species and, second, antenna chlorophyll-proteins are the first target of high light damages. When photoprotection mechanisms become insufficient, the antenna chlorophyll proteins act as fuses: LHCI chlorophylls are degraded while the reaction center photochemical activity is maintained. Differences with respect to photoprotection strategy in Photosystem II, where the reaction center is the first target of photoinhibition, are discussed.


Plant Cell and Environment | 2011

Role of PSBS and LHCSR in Physcomitrella patens acclimation to high light and low temperature.

Caterina Gerotto; Alessandro Alboresi; Giorgio M. Giacometti; Roberto Bassi; Tomas Morosinotto

Photosynthetic organisms respond to strong illumination by activating several photoprotection mechanisms. One of them, non-photochemical quenching (NPQ), consists in the thermal dissipation of energy absorbed in excess. In vascular plants NPQ relies on the activity of PSBS, whereas in the green algae Chlamydomonas reinhardtii it requires a different protein, LHCSR. The moss Physcomitrella patens is the only known organism in which both proteins are present and active in triggering NPQ, making this organism particularly interesting for the characterization of this protection mechanism. We analysed the acclimation of Physcomitrella to high light and low temperature, finding that these conditions induce an increase in NPQ correlated to overexpression of both PSBS and LHCSR. Mutants depleted of PSBS and/or LHCSR showed that modulation of their accumulation indeed determines NPQ amplitude. All mutants with impaired NPQ also showed enhanced photosensitivity when exposed to high light or low temperature, indicating that in this moss the fast-responding NPQ mechanism is also involved in long-term acclimation.


Proceedings of the National Academy of Sciences of the United States of America | 2016

Flavodiiron proteins act as safety valve for electrons in Physcomitrella patens

Caterina Gerotto; Alessandro Alboresi; Andrea Meneghesso; Martina Jokel; Marjaana Suorsa; Eva-Mari Aro; Tomas Morosinotto

Significance Photosynthesis regulation is fundamental to responding to environmental dynamic changes and avoiding oxidative damage. These regulatory mechanisms were shaped during evolution from cyanobacteria to plants, as well as after the colonization of new habitats. Land colonization was a key phase in evolution with plants capable of adapting to drastically different conditions with respect to their aquatic ancestors. Valuable information on this adaptation can be obtained studying nonvascular plants, such as the moss Physcomitrella patens, that diverged from flowering plants early after land colonization. Here we show that in P. patens, Flavodiiron (FLV) proteins are acting as an electron sink to avoid photosynthetic electron transport chain over-reduction after any increase in illumination and are fundamental for protection under fluctuating light conditions. Photosynthetic organisms support cell metabolism by harvesting sunlight to fuel the photosynthetic electron transport. The flow of excitation energy and electrons in the photosynthetic apparatus needs to be continuously modulated to respond to dynamics of environmental conditions, and Flavodiiron (FLV) proteins are seminal components of this regulatory machinery in cyanobacteria. FLVs were lost during evolution by flowering plants, but are still present in nonvascular plants such as Physcomitrella patens. We generated P. patens mutants depleted in FLV proteins, showing their function as an electron sink downstream of photosystem I for the first seconds after a change in light intensity. flv knock-out plants showed impaired growth and photosystem I photoinhibition when exposed to fluctuating light, demonstrating FLV’s biological role as a safety valve from excess electrons on illumination changes. The lack of FLVs was partially compensated for by an increased cyclic electron transport, suggesting that in flowering plants, the FLV’s role was taken by other alternative electron routes.

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