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Transcription of protein-encoding genes starts with forming a pre-initiation complex comprised of RNA polymerase II and several general transcription factors. To activate gene expression, transcription factors must overcome repressive chromatin structure, which is accomplished with multiprotein complexes. One such complex, SAGA, modifies the nucleosomal histones through acetylation and other histone modifications. A prototypical histone acetyltransferase (HAT) known as general control non-repressed protein 5 (GCN5), was defined biochemically as the first transcription-linked HAT with specificity for histone H3 lysine 14. In this review, we analyze the components of the putative plant SAGA complex during plant evolution, and current knowledge on the biological role of the key components of the HAT module, GCN5 and ADA2b in plants, will be summarized.

Olive tree growth and reproduction are severely affected by temperature extremes, compromising fruit yield. In that aspect, the olive varieties “Koroneiki” and “Mastoidis” were employed in a mild cold stress experiment, imitating night frost incidents to assess their biochemical, physiological and reproductive functions in relation to genotype. The physiological performance of the stressed plants was not significantly altered, suggesting that both cultivars were well adapted to mild cold night stress. The biochemical response of the plants, regarding antioxidant enzymes, H2O2 and TBARS accumulation, confirmed that both cultivars could cope with the stress applied. The mRNA levels of the PPO gene, which participates in hydroxytyrosol biosynthesis and plant defense, were elevated after 24-h stress at 0 °C, in both cultivars with “Mastoidis” plants exhibiting higher levels for a longer period. Three more genes involved in hydroxytyrosol biosynthesis upregulated their expression levels as a response to cold stress. The numerous plant phenology aspects measured reinforced the conclusion that both cultivars responded to the stress applied. The results of the present study may contribute to better understanding olive tree adaptive responses to low temperature events, an abiotic stress condition that is often present in an open plantation, thus assisting farmers on breeding and cultivar selection.

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Histone acetylation is directly related to gene expression. In yeast, the acetyltransferase general control nonderepressible-5 (GCN5) targets histone H3 and associates with transcriptional co-activators alteration/deficiency in activation-2 (ADA2) and alteration/deficiency in activation-3 (ADA3) in complexes like SAGA. Arabidopsis thaliana has two genes encoding proteins, designated ADA3a and ADA3b, that correspond to yeast ADA3. We investigated the role of ADA3a and ADA3b in regulating gene expression during flowering time. Specifically, we found that knock out mutants ada3a-2 and the double mutant ada3a-2 ada3b-2 lead to early flowering compared to the wild type plants under long day (LD) conditions and after moving plants from short days to LD. Consistent with ADA3a being a repressor of floral initiation, FLOWERING LOCUS T (FT) expression was increased in ada3a mutants. In contrast, other genes involved in multiple pathways leading to floral transition, including FT repressors, players in GA signaling, and members of the SPL transcriptional factors, displayed reduced expression. Chromatin immunoprecipitation analysis revealed that ADA3a affects the histone H3K14 acetylation levels in SPL3, SPL5, RGA, GAI, and SMZ loci. In conclusion, ADA3a is involved in floral induction through a GCN5-containing complex that acetylates histone H3 in the chromatin of flowering related genes.

Peppers are the fourth most important vegetable in the global food economy. Greek pepper cultivars 'Florinis' and 'Karatzova' are especially popular because of the signature red color and sweet taste of the fruits. The economic interest in 'Florinis' peppers has led to many adulteration events. In that aspect, genetic profiles of 'Florinis', a 'Florinis'-type and 'Karatzova' peppers, were studied using Inter Simple Sequence Repeats (ISSR) molecular markers and an automated fragment detection system. Biochemical parameters, such as total dietary fiber, total phenolic and lycopene contents, and sugar profile that affect the fruit organoleptic and nutritional properties were evaluated. The molecular protocol established during this study may successfully discriminate the original 'Florinis' cultivar from the 'Florinis'-type peppers. 'Karatzova' cultivar, which fruits are similar to 'Florinis', presented also a unique profile. The biochemical evaluation revealed that 'Florinis' peppers had the highest sweetness index and total phenolic content. Such an analysis could be used for the discrimination of pepper cultivars sharing common morphological traits ensuring the unique identity of each cultivar and protecting farmers and consumers from fraud.

Analysis of table olives microbiome using next-generation sequencing has enriched the available information about the microbial community composition of this popular fermented food. In this study, 16S and 18S rRNA sequencing was performed on table olives of five Greek popular cultivars, Halkidikis, Thassou, Kalamon, Amfissis, and Konservolia, fermented either by Greek style (in brine or salt-drying) or by Spanish style, in order to evaluate their microbial communities. Moreover, analytical methods were used to evaluate their biochemical properties. The prevailing bacterial species of all olives belonged to Lactobacillaceae, Leuconostocaceae, and Erwiniaceae families, while the most abundant yeasts were of the Pichiaceae family. Principal coordinates analysis showed a clustering of samples cured by salt-drying and of samples stored in brine, regardless of their cultivar. The biochemical evaluation of total phenol content, antioxidant activity, hydroxytyrosol, oleuropein, oleocanthal, and oleacein showed that salt-dried olives had low amounts of hydroxytyrosol, while Spanish-style green olives had the highest amounts of oleocanthal. All the other values exhibited various patterns, implying that more than one factor affects the biochemical identity of the final product. The protocols applied in this study can provide useful insights for the final product, both for the producers and the consumers.

Almonds are one of the most popular nuts, cultivated in countries with Mediterranean climates. In an almond orchard of the self-incompatible cultivar ‘Ferragnes’ in Greece, a tree with different morphological characteristics and signs of self-compatibility was observed. The aim of this study was to study the phenotype, investigate the self-compatibility trait, and elucidate the phylogenetic background of this tree, named ‘Mars’. Morphological traits and kernel and nut characteristics were measured in ‘Mars’, ‘Ferragnes’, ‘Tuono’, and ‘Lauranne’ cultivars. The self-compatibility trait of almonds is attributed to the Sf allele; thus, its existence was investigated in ‘Mars’ by PCR amplification. Moreover, the S-RNase genes of all the cultivars were sequenced. The genetic profile of ‘Mars’ was identified using eight SSR molecular markers and compared with the ‘Ferragnes’, ‘Ferraduel’, ‘Texas’, ‘Tuono’, and ‘Lauranne’ cultivars. The morphological traits suggest that ‘Mars’ is more similar to the ‘Ferragnes’ cultivar, while it bears the Sf allele. S-RNases sequencing revealed that ‘Mars’ has the genotype S1Sf, and the SSR markers showed that it is differentiated genetic material, suggesting it is a cross between ‘Ferragnes’ and ‘Tuono’. Therefore, ‘Mars’ is evaluated as a self-compatible variety with interesting agronomic traits for use in new mono-cultivar almond plantations.