Solar UV-B Radiation Influences Carotenoid Accumulation of Tomato Fruit through Both Ethylene-Dependent and -independent Mechanisms

The effect of UV-B shielding on ethylene production in ripening tomato fruits and the contribution of ethylene and UV-B radiation on carotenoid accumulation and profile during ripening were assessed to get more insight about the interplay between these two regulatory factors. To this aim, rin and nor tomato mutants, unable to produce ripening ethylene, and cv Ailsa Craig were cultivated under control or UV-B depleted conditions until full fruit ripening. The significantly decreased ethylene evolution following UV-B depletion, evident only in Ailsa Craig, suggested the requirement of functional rin and nor genes for UVB-mediated ethylene production. Carotenoid content and profile were found to be controlled by both ethylene and UV-B radiation. This latter influenced carotenoid metabolism either in an ethylene-dependent or -independent way, as indicated by UVB-induced changes also in nor and rin carotenoid content and confirmed by correlation plots between ethylene evolution and carotenoid accumulation performed separately for control and UV-B shielded fruits. In conclusion, natural UV-B radiation influences carotenoid metabolism in a rather complex way, involving ethylene-dependent and -independent mechanisms, which seem to act in an antagonistic way

Flavonoid profiling and biosynthetic gene expression in flesh and peel of two tomato genotypes grown under UV-B-depleted conditions during ripening

The aim of this study was to evaluate the effect of shielding solar ultraviolet B radiation on the accumulation of some flavonoids and their precursors hydroxycinnamic acids in tomato (Solanum lycopersicum) using LC-ESI-MS/MS. In particular, flesh and peel of two tomato hybrids, DRW 5981 and Esperanza, were separately analysed. The hybrids have been chosen on account of their different response to the light, since it was previously reported that they show a different pigmentation and an opposite behaviour under UV-B in terms of carotenoids and ascorbic acid content at different ripening stages. To determine the effect of UV-B radiation during tomato ripening, we also measured the expression of some flavonoid biosynthetic genes by Real Time RT-PCR analysis. The results here presented allowed us to conclude that UV-B radiation deeply and differentially affect the content of the considered flavonoids and hydroxycinnamic acids as well as the expression of some of their biosynthetic genes in both flesh and peel during the ripening process. On the other hand, the collected data clearly showed that this influence varies between different genotypes. We conclude that the use of specific plastic covers able to eliminate UV-B radiation may be an environmental-friendly approach to modulate the expression of structural genes and, in turn, to enhance healthy antioxidant compounds in fruits of specific tomato cultivars

The AtMYB11 gene from Arabidopsis is expressed in meristematic cells and modulates growth in planta and organogenesis in vitro

In plants, MYB transcription factors play important roles in many developmental processes including cell cycle progression, cell differentiation and lateral organ polarity. Here we show that the R2R3-MYB AtMYB11 gene is expressed in root and shoot meristems and also in young still meristematic leaf and flower primordia of Arabidopsis. Knock-out atmyb11-I mutants and RNAi plants germinate faster, show a faster hypocotyl and primary root elongation, develop more lateral and adventitious roots, show faster development of inflorescence, and initiate more lateral inflorescences and fruits than wild-type plants. The opposite phenotype was displayed by plants overexpressing AtMYB11. De novo formation of root meristemoids, and consequently macroscopic roots, from thin cell layers cultured in vitro was enhanced in explants from atmyb11-I and reduced in those from lines overexpressing AtMYB11. These findings indicate that AtMYB11 modulates overall growth in plants by reducing the proliferation activity of meristematic cells and delaying plant development

Solar UV-B radiation influences carotenoid accumulation of tomato fruit through both ethylene-dependent and -independent mechanisms

The effect of UV-B shielding on ethylene production in ripening tomato fruits and the contribution of ethylene and UV-B radiation on carotenoid accumulation and profile during ripening were assessed to get more insight about the interplay between these two regulatory factors. To this aim, rin and nor tomato mutants, unable to produce ripening ethylene, and cv Ailsa Craig were cultivated under control or UV-B depleted conditions until full fruit ripening. The significantly decreased ethylene evolution following UV-B depletion, evident only in Ailsa Craig, suggested the requirement of functional rin and nor genes for UVB-medlated ethylene production. Carotenoid content and profile were found to be controlled by both ethylene and UV-B radiation. This latter Influenced carotenoid metabolism either in an ethylene-dependent or -independent way, as indicated by UVB-induced changes also in nor and rin carotenoid content and confirmed by correlation plots between ethylene evolution and carotenoid accumulation performed separately for control and UV-B shielded fruits. In conclusion, natural UV-B radiation influences carotenoid metabolism in a rather complex way, involving ethylene-dependent and -independent mechanisms, which seem to act in an antagonistic way

NUCLEAR FACTOR Y, subunit A (NF-YA) proteins positively regulate flowering and act through FLOWERING LOCUS T

Photoperiod dependent flowering is one of several mechanisms used by plants to initiate the developmental transition from vegetative growth to reproductive growth. The NUCLEAR FACTOR Y (NF-Y) transcription factors are heterotrimeric complexes composed of NF-YA and histone-fold domain (HFD) containing NF-YB/NF-YC, that initiate photoperiod-dependent flowering by cooperatively interacting with CONSTANS (CO) to drive the expression of FLOWERING LOCUS T (FT). This involves NF-Y and CO binding at distal CCAAT and proximal “CORE” elements, respectively, in the FT promoter. While this is well established for the HFD subunits, there remains some question over the potential role of NF-YA as either positive or negative regulators of this process. Here we provide strong support, in the form of genetic and biochemical analyses, that NF-YA, in complex with NF-YB/NF-YC proteins, can directly bind the distal CCAAT box in the FT promoter and are positive regulators of flowering in an FT-dependent manner.This work was funded by the National Science Foundation (US, http://www.nsf.gov/) award 1149822 to BFH. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ye

Functional analysis of NF-Y transcription factors in Arabidopsis

In yeast and mammals, the CCAAT box, one of the most promoter ubiquitous elements, is recognized by NF-Y, a trimer composed by NF-YA, NF-YB and NF-YC, all required for DNA-binding and encoded by single copy genes. In Arabidopsis thaliana 29 NF-Y genes have been cloned: 10 NF-YAs, 10 NF-YBs, 9 NF-Ycs. The aim of this Ph.D project has been the functional characterisation of some members of this gene family. To determine the function of these transcription factors, various approaches have been undertaken such as analysis of expression pattern, mutant and double mutants selection, production of transgenic plants in which the selected NF-Y gene is silenced by RNA interferences technics or ectopically expressed. Moreover, interactions among NF-Y subunits have been studied. Two-Hybrid analysis indicates that all B subunit are able to interact with C subunit tested and the colorimetric assay indicates that some interaction are favourite in comparison to others. Some of these data have been confirmed by biochemical assays