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[EN] Carotenoids are C40 isoprenoids with well-established roles in photosynthesis, pollination, photoprotection, and hormone biosynthesis. The enzymatic or ROS-induced cleavage of carotenoids generates a group of compounds named apocarotenoids, with an increasing interest by virtue of their metabolic, physiological, and ecological activities. Both classes are used industrially in a variety of fields as colorants, supplements, and bio-actives. Crocins and picrocrocin, two saffron apocarotenoids, are examples of high-value pigments utilized in the food, feed, and pharmaceutical industries. In this study, a unique construct was achieved, namely O6, which contains CsCCD2L, UGT74AD1, and UGT709G1 genes responsible for the biosynthesis of saffron apocarotenoids driven by a patatin promoter for the generation of potato tubers producing crocins and picrocrocin. Different tuber potatoes accumulated crocins and picrocrocin ranging from 19.41-360 to 105-800 mu g/g DW, respectively, with crocetin, crocin 1 [(crocetin-(beta-D-glucosyl)-ester)] and crocin 2 [(crocetin)-(beta-D-glucosyl)-(beta-D-glucosyl)-ester)] being the main compounds detected. The pattern of carotenoids and apocarotenoids were distinct between wild type and transgenic tubers and were related to changes in the expression of the pathway genes, especially from PSY2, CCD1, and CCD4. In addition, the engineered tubers showed higher antioxidant capacity, up to almost 4-fold more than the wild type, which is a promising sign for the potential health advantages of these lines. In order to better investigate these aspects, different cooking methods were applied, and each process displayed a significant impact on the retention of apocarotenoids. More in detail, the in vitro bioaccessibility of these metabolites was found to be higher in boiled potatoes (97.23%) compared to raw, baked, and fried ones (80.97, 78.96, and 76.18%, respectively). Overall, this work shows that potatoes can be engineered to accumulate saffron apocarotenoids that, when consumed, can potentially offer better health benefits. Moreover, the high bioaccessibility of these compounds revealed that potato is an excellent way to deliver crocins and picrocrocin, while also helping to improve its nutritional value., This work was supported by grants BIO2016-77000-R and PIB2020-114761RB-I00 from Ministerio de Ciencia e Innovacion (MCIN), SBPLY/17/180501/000234 and SBPLY/21/180501/000012 from the Junta de Comunidades de Castilla-La Mancha (co-financed European Union FEDER funds) to LG and OA, and SBPLY/17/180501/000229 and SBPLY/21/180501/000064 from the Junta de Comunidades de Castilla-La Mancha (co-financed European Union FEDER funds) to RL and Margarita Salas fellowship from Ministerio de Universidades and Universidad de Castilla-La Mancha to AM-B. JR was supported by the Spanish Ministry of Science and Innovation through a "Juan de la Cierva-Incorporacion" grant (IJC2020-045612-I).

Potato bacterial wilt is caused by the devastating bacterial pathogen Ralstonia solanacearum. Quantitative resistance to this disease has been and is currently introgressed from a number of wild relatives into cultivated varieties through laborious breeding programs. Here, we present two methods that we have developed to facilitate the screening for resistance to bacterial wilt in potato. The first one uses R. solanacearum reporter strains constitutively expressing the luxCDABE operon or the green fluorescent protein (gfp) to follow pathogen colonization in potato germplasm. Luminescent strains are used for nondestructive live imaging, while fluorescent ones enable precise pathogen visualization inside the plant tissues through confocal microscopy. The second method is a BIO-multiplex-PCR assay that is useful for sensitive and specific detection of viable R. solanacearum (IIB-1) cells in latently infected potato plants. This BIO-multiplex-PCR assay can specifically detect IIB-1 sequevar strains as well as strains belonging to all four R. solanacearum phylotypes and is sensitive enough to detect without DNA extraction ten bacterial cells per mL in complex samples.The described methods allow the detection of latent infections in roots and stems of asymptomatic plants and were shown to be efficient tools to assist potato breeding programs.

The results obtained in this thesis indicate that StNAC103 promoter activity is induced in tissues undergoing suberin synthesis. Moreover StNAC103 transcript accumulation is concomitant to that of CYP86A33 and takes place after that of FHT. Nonetheless, an increase of the suberin and wax accumulation in the silenced periderms for StNAC103 suggests its role as a repressor in suberin and wax accumulation. Altogether these studies support the hypothesis that there exists a very fine regulation of the suberin and wax synthesis in the periderm, in which StNAC103 plays an important role. Els resultats obtinguts en aquesta tesi indiquen que l’activitat del promotor d’StNAC103 s’indueix en teixits on és activa la síntesi de suberina i l’acumulació del transcrit corresponent es dóna concomitantment a la de l'ω-hidroxilasa d’acids grassos CYP86A33 i s’inicia posteriorment a la de la feruloïl transferasa d’ω-hidroxiacids i alcohols FHT. Tanmateix, l’augment en l’acumulació de suberina i ceres en els peridermes silenciats per StNAC103 suggereix un paper repressor d’aquest factor de transcripció. Tot plegat fa pensar que hi ha d’haver una regulació molt fina de la síntesi de suberina i ceres en el periderma i que StNAC103 hi té un paper destacat. Aquesta tesi s’ha dut a terme amb el suport de la Generalitat de Catalunya (Beques i Ajuts per a la formació i contractació de personal investigador novell. Convocatòria 2008 – FI 2009) i del Ministerio de Educación y Ciencia (projecte finançat AGL2006-07342, AGL2009-13745)

La peridermis és una estructura complexa que protegeix els òrgans vegetals madurs (secundaris) i les zones que han sofert ferides de la pèrdua d'aigua i dels patògens. Aquesta funció barrera és deguda al fel·lema o súber, un teixit format per cèl·lules suberificades. Tant el fel·lema com la suberina són crucials per la vida de les plantes terrestres, però pràcticament no es coneix res dels processos moleculars que regulen la seva formació, probablement degut a la manca de models adequats. En aquesta tesi s'han identificat i caracteritzat gens induïts al fel·lema mitjançant la combinació de dues plantes models. L'escorça d'alzina surera (Quercus suber) s'ha utilitzat per aïllar gens candidats de la formació del fel·lema i per investigar el comportament d'alguns d'aquests gens durant l'estació de creixement, mentre que la pela de la patata (Solanum tuberosum) s'ha utilitzat en estudis de genètica reversa per demostrar la funció d'alguns gens reguladors al fel·lema., The periderm is a complex structure that protects plant mature (secondary) organs and wounded tissues from water loss, injuries and pathogens. This barrier capacity is accomplished by the cork layer of the periderm, a tissue made of dead cells with suberin deposited into cell walls. Although cork and suberin are critical for the survival of land plants, very few is known about the molecular processes involved in their biosynthesis and differentiation, probably due to the lack of appropriate plant models. Here we developed a strategy to identify and characterize cork candidate genes using a combination of two model plants for periderm studies. The bark of cork oak (Quercus suber) was used to identify candidate genes and to analyze the seasonal behaviour of some of these genes. The potato (Solanum tuberosum) tuber was used to demonstrate the role of some selected candidates in the regulation of cork by reverse genetic analyses.