In addition to the full-length transcript ARF8.1, a splice variant (ARF8.2) of the auxin response factor gene ARF8 has been reported. Here, we identified an intron-retaining variant of ARF8.2, ARF8.4, whose translated product is imported into the nucleus and has tissue-specific localization in Arabidopsis thaliana. By inducibly expressing each variant in arf8-7 flowers, we show that ARF8.4 fully complements the short-stamen phenotype of the mutant and restores the expression of AUX/IAA19, encoding a key regulator of stamen elongation. By contrast, the expression of ARF8.2 and ARF8.1 had minor or no effects on arf8-7 stamen elongation and AUX/IAA19 expression. Coexpression of ARF8.2 and ARF8.4 in both the wild type and arf8-7 caused premature anther dehiscence: We show that ARF8.2 is responsible for increased expression of the jasmonic acid biosynthetic gene DAD1 and that ARF8.4 is responsible for premature endothecium lignification due to precocious expression of transcription factor gene MYB26. Finally, we show that ARF8.4 binds to specific auxin-related sequences in both the AUX/IAA19 and MYB26 promoters and activates their transcription more efficiently than ARF8.2. Our data suggest that ARF8.4 is a tissue-specific functional splice variant that controls filament elongation and endothecium lignification by directly regulating key genes involved in these processes.

Plant cell cultures as valuable tools for the production of specific metabolites can be greatly improved by the application of elicitors including cyclodextrins (CDs) for enhancing the yields of the desired plant compounds. Here the effects of 2,6-dimethyl-β-cyclodextrins (DIMEB) on the production of carotenoids and quinones from Artemisia annua L. cell suspension cultures were investigated. The addition of 50 mM DIMEB induced an early increase of intracellular carotenoid and quinone contents, which could be observed to a higher extent for lutein (10-fold), Q9 (3-fold) and Q10 (2.5-fold). Real Time PCR analysis revealed that the expression of 1-deoxy-d-xylulose-5-phosphate reductoisomerase (DXR) gene in DIMEB treated cell cultures after three days was 2.5-fold higher than in untreated samples, thus suggesting that the DIMEB induced increase of carotenoids and quinones could be due to the induction of the plastidial isoprenoid biosynthetic route. In addition, the DIMEB treatment induced an enhanced release of carotenoids and quinones into the culture medium of A. annua cell suspension cultures possibly due to the ability of CDs to form inclusion complexes with hydrophobic molecules.

This review is dedicated to the memory of Prof. Domenico Mariotti, who significantly contributed to establishing the Italian research community in Agricultural Genetics and carried out the first experiments of Agrobacterium-mediated plant genetic transformation and regeneration in Italy during the 1980s. Following his scientific interests as guiding principles, this review summarizes the recent advances obtained in plant biotechnology and fundamental research aiming to: (i) Exploit in vitro plant cell and tissue cultures to induce genetic variability and to produce useful metabolites; (ii) gain new insights into the biochemical function of Agrobacterium rhizogenes rol genes and their application to metabolite production, fruit tree transformation, and reverse genetics; (iii) improve genetic transformation in legume species, most of them recalcitrant to regeneration; (iv) untangle the potential of KNOTTED1-like homeobox (KNOX) transcription factors in plant morphogenesis as key regulators of hormonal homeostasis; and (v) elucidate the molecular mechanisms of the transition from juvenility to the adult phase in Prunus tree species.

Artemisia annua L. is well-known as the plant source of artemisinin, a sesquiterpene lactone with effective antimalarial activity. Here, a putative ortholog of the Arabidopsis thaliana WRKY40 transcription factor (TF) was isolated via reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends in A. annua and named AaWRKY40. A putative nuclear localization domain was identified in silico and experimentally confirmed by using protoplasts of A. annua transiently transformed with AaWRKY40-GFP. A genome-wide analysis identified 122 WRKY genes in A. annua, and a manually curated database was obtained. The deduced proteins were categorized into the major WRKY groups, with group IIa containing eight WRKY members including AaWRKY40. Protein motifs, gene structure, and promoter regions of group IIa WRKY TFs of A. annua were characterized. The promoter region of AaWRKY group IIa genes contained several abiotic stress cis-acting regulatory elements, among which a highly conserved W-box motif was identified. Expression analysis of AaWRKY40 compared to AaWRKY1 in A. annua cell cultures treated with methyl jasmonate known to enhance artemisinin production, suggested a possible involvement of AaWRKY40 in terpenoid metabolism. Further investigation is necessary to study the role of AaWRKY40 and possible interactions with other TFs in A. annua.

The olive oil is an unfavorable substrate for microbial survival and growth. Only few microorganisms use olive oil fatty acids as carbon and energy sources, and survive in the presence of olive oil anti-microbial components. In this study, we have evaluated the occurrence of microorganisms in 1-year-stored extra-virgin olive oil samples. We detected the presence of bacterial and yeast species with a recurrence of the bacterium Stenotrophomonas rhizophila and yeast Sporobolomyces roseus. We then assayed the ability of all isolates to grow in a mineral medium supplemented with a commercial extra-virgin olive oil as a sole carbon and energy source, and analyzed the utilization of olive oil fatty acids during their growth. We finally focused on two bacterial isolates belonging to the species Pantoea septica. Both these isolates produce carotenoids, and one of them synthesizes bioemulsifiers enabling the bacteria to better survive/growth in this unfavorable substrate. Analyses point to a mixture of glycolipids with glucose, galactose and xylose as carbohydrate moieties whereas the lipid domain was constituted by C6-C10 β-hydroxy carboxylic acids.