The distinctive acidity of citrus fruit is determined by a regulatory complex of MYB and bHLH transcription factors together with a WDR protein (MBW complex) which operates in the unique juice vesicles of the fruit. We describe a mutation affecting the MYB protein, named Nicole, in sweet orange and identify its target genes that determine hyperacidification, specifically. We propose that the acidity, typical of citrus fruits, was the result of a loss of the ability of Nicole to activate the gene encoding anthocyanidin reductase, an enzyme essential for the synthesis of proanthocyanidins, which are absent in citrus fruit.
View Article and Find Full Text PDFCarotenoid-rich foods such as citrus fruits have a wide range of functions in human health. They primarily exert antioxidant effects, but individual carotenoids may also act through other health-promoting mechanisms such as β-carotene as pro-vitamin A. Here, we show that red-fleshed sweet oranges grown in tropical climates are 4-9 times richer in carotenoids than their orange-fleshed counterparts, regardless of their maturation stage.
View Article and Find Full Text PDFThe Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a key vector of the phloem-limited bacteria Candidatus Liberibacter asiaticus (CLas) associated with huanglongbing (HLB), the most serious and currently incurable disease of citrus worldwide. Here we report the first investigation into the potential use of a spider venom-derived recombinant neurotoxin, ω/κ-HxTx-Hv1h (hereafter HxTx-Hv1h) when delivered alone or when fused to snowdrop lectin (Galanthus nivalis agglutinin; GNA) to control D. citri.
View Article and Find Full Text PDFFood Chem (Oxf)
December 2022
orange juice is an excellent dietary source of β-carotene, a well-known antioxidant. However, β-carotene concentrations are relatively low in most cultivars. We developed a new orange through metabolic engineering strategy (GS) with 33.
View Article and Find Full Text PDFHuanglongbing (HLB), the most destructive citrus disease, is associated with unculturable, phloem-limited Liberibacter species, mainly L. asiaticus (Las). Las is transmitted naturally by the insect .
View Article and Find Full Text PDFBackground: Host genetic resistance is a promising strategy for the management of Diaphorina citri Kuwayama (Hemiptera: Psyllidae), and consequently Huanglongbing (HLB). To date, no study has investigated the resistance to D. citri in the clonal and vegetatively propagated plants of the Microcitrus, Eremocitrus, and Atalantia genera.
View Article and Find Full Text PDFTo recover transgenic citrus plants in the most efficient manner, the use of selection marker genes is essential. In this work, it was shown that the mutated forms of the acetolactate synthase () gene in combination with the herbicide selection agent imazapyr (IMZ) added to the selection medium may be used to achieve this goal. This approach enables the development of cisgenic regenerants, namely, plants without the incorporation of those bacterial genes currently employed for transgenic selection, and additionally it allows the generation of edited, non-transgenic plants with altered endogenous genes leading to IMZ resistance.
View Article and Find Full Text PDFKnowledge on diseases caused by Citrus tristeza virus (CTV) has greatly increased in last decades after their etiology was demonstrated in the past seventies. Professor Ricardo Flores substantially contributed to these advances in topics like: i) improvement of virus purification to obtain biologically active virions, ii) sequencing mild CTV isolates for genetic comparisons with sequences of moderate or severe isolates and genetic engineering, iii) analysis of genetic variation of both CTV genomic RNA ends and features of the highly variable 5' end that allow accommodating this variation within a conserved secondary structure, iv) studies on the structure, subcellular localization and biological functions of the CTV-unique p23 protein, and v) potential use of p23 and other 3'-proximal regions of the CTV genome to develop transgenic citrus resistant to the virus. Here we review his main achievements on these topics and how they contributed to deeper understanding of CTV biology and to new potential measures for disease control.
View Article and Find Full Text PDFNumerous studies have revealed the remarkable health-promoting activities of citrus fruits, all of them related to the accumulation of bioactive compounds, including vitamins and phytonutrients. Anthocyanins are characteristic flavonoids present in blood orange, which require low-temperature for their production. Storage at low-temperature of blood oranges has been proven to be a feasible postharvest strategy to increase anthocyanins in those countries with warm climates.
View Article and Find Full Text PDFHuanglongbing (HLB), formerly known as greening, is a bacterial disease restricted to some Asian and African regions until two decades ago. Nowadays, associated bacteria and their vectors have spread to almost all citrus-producing regions, and it is currently considered the most devastating citrus disease. HLB management can be approached in terms of prevention, limiting or avoiding pathogen and associated vectors to reach an area, or in terms of control, trying to reduce the impact of the disease by adopting different cultural strategies depending on infestation/infection levels.
View Article and Find Full Text PDFBackground: Candidatus Liberibacter asiaticus (CLas) is one the causative agents of greening disease in citrus, an unccurable, devastating disease of citrus worldwide. CLas is vectored by Diaphorina citri, and the understanding of the molecular interplay between vector and pathogen will provide additional basis for the development and implementation of successful management strategies. We focused in the molecular interplay occurring in the gut of the vector, a major barrier for CLas invasion and colonization.
View Article and Find Full Text PDFThe Asian citrus psyllid, , is the vector of the bacterium " Liberibacter asiaticus" (Las), associated with the devastating, worldwide citrus disease huanglongbing. In order to explore the molecular interactions of this bacterium with during the vector acquisition process, cDNA libraries were sequenced on an Illumina platform, obtained from the gut of adult psyllids confined in healthy (H) and in Las-infected young shoots (Las) for different periods of times (I = 1/2 days, II = 3/4 days, and III = 5/6 days). In each sampling time, three biological replicates were collected, containing 100 guts each, totaling 18 libraries depleted in ribosomal RNA.
View Article and Find Full Text PDFHuanglongbing (HLB) disease is threatening the sustainability of citriculture in affected regions because of its rapid spread and the severity of the symptoms it induces. Herein, we summarise the main research findings that can be exploited to develop HLB-resistant cultivars. A major bottleneck has been the lack of a system for the ex vivo cultivation of HLB-associated bacteria (CLs) in true plant hosts, which precludes the evaluation of target genes/metabolites in reliable plant/pathogen/vector environments.
View Article and Find Full Text PDFHuanglongbing is a highly destructive citrus disease associated with " Liberibacter asiaticus" (Las), a phloem-limited and non-culturable bacterium, naturally transmitted by the psyllid Although diverse approaches have been used to understand the molecular mechanisms involved in the pathogen-host interaction, such approaches have focused on already infected and/or symptomatic plants, missing early events in the initial days post-inoculation. This study aimed to identify the time course of Las multiplication and whole-plant colonization immediately following inoculation by infected psyllids feeding for 2 days. Thus, the experimental approach was to track Las titers after psyllid inoculation in new shoots (NS) of (susceptible), (partially resistant), and (fully resistant).
View Article and Find Full Text PDFFront Plant Sci
March 2021
Huanglongbing (HLB) is a destructive disease, associated with psyllid-transmitted phloem-restricted pathogenic bacteria, which is seriously endangering citriculture worldwide. It affects all citrus species and cultivars regardless of the rootstock used, and despite intensive research in the last decades, there is no effective cure to control either the bacterial species ( Liberibacter spp.) or their insect vectors ( and ).
View Article and Find Full Text PDFHuanglongbing (HLB) is the most destructive, yet incurable disease of citrus. Finding sources of genetic resistance to HLB-associated ' Liberibacter asiaticus' (Las) becomes strategic to warrant crop sustainability, but no resistant genotypes exist. Some relatives of the family Rutaceae, subfamily Aurantioideae, were described as full-resistant to Las, but they are phylogenetically far, thus incompatible with .
View Article and Find Full Text PDFAnthocyanins are pigments present in blood oranges which can be enriched by post-harvest cold storage. Additionally, citrus fruits contain appreciable levels of other flavonoids, whose content increases under post-harvest heat treatments. Here, we investigated the effects of curing (37 °C for 3 days) and storage at low-temperature (9 °C) during 15, 30 and 45 days on accumulation of anthocyanins and other flavonoids in Moro and Sanguinelli Polidori blood oranges (Citrus sinensis L.
View Article and Find Full Text PDFPLoS One
September 2020
In several phytophagous hemipterans, behavior appears to be mediated by both visual and chemical cues. For the Asian citrus psyllid (ACP) Diaphorina citri (Hemiptera: Liviidae), olfactometric assays are generally difficult to interpret owing to the low proportion of individuals responding to odors (~30-40%), which compromises the efficiency and reliability of the results of behavioral tests. In the present study, the ACP behavioral response to emitted odors from sweet orange (Citrus sinensis L.
View Article and Find Full Text PDFand are aurantioid hosts of the Asian citrus psyllid (ACP) , the principal vector of ' Liberibacter asiaticus' (Las). Las is the pathogen associated with huanglongbing (HLB), the Asian form of which is the most devastating disease of species and cultivars (Rutaceae: Aurantioideae). is a common ornamental and is grown as an ornamental, a citrus rootstock, and a hedgerow fence plant.
View Article and Find Full Text PDFConventional breeding of citrus types demands a long-term effort due to their complex reproductive biology and long juvenile period. As a compelling alternative, genetic engineering of mature tissues allows the insertion of specific traits into specific elite cultivars, including well-known and widely grown varieties and rootstocks, thus reducing the time and costs involved in improving and evaluating them. Conventional breeding for resistance to CTV in citrus varieties has been largely unsuccessful as well as cloning of the genes conferring resistance to specific citrus types.
View Article and Find Full Text PDFTo dissect the host RNA silencing response incited by citrus tristeza virus (CTV, genus Closterovirus), a (+) ssRNA of ~19300 nt, and the counter reaction deployed by the virus via its three RNA silencing suppressors (RSS), the small RNAs (sRNAs) of three virus-host combinations were deep sequenced. The subsequent analysis indicated that CTV sRNAs (1) constitute more than half of the total sRNAs in the susceptible Mexican lime and sweet orange, while only 3.5% in the restrictive sour orange; (2) are mostly of 21-22 nt, with those of (+) sense predominating slightly; and (3) derive from all the CTV genome, as evidenced by its entire recomposition from viral sRNA contigs but adopt an asymmetric pattern with a hotspot mapping at the 3'-terminal ~2500 nt.
View Article and Find Full Text PDF'Cara Cara' is a red orange ( (L.) Osbeck) variety originally from Venezuela characterized by a significantly higher and diversified carotenoid content including higher-concentration lycopene, -E--carotene, phytoene, and other carotenoids when compared with the carotenoid profile of its isogenic blond counterpart 'Bahia', also known as Washington navel. The exceptionally high carotenoid content of 'Cara Cara' is of special interest due to its neuroprotective potential.
View Article and Find Full Text PDFNovel, suitable and sustainable alternative control tactics that have the potential to reduce migration of Diaphorina citri into commercial citrus orchards are essential to improve management of huanglongbing (HLB). In this study, the effect of orange jasmine (Murraya paniculata) as a border trap crop on psyllid settlement and dispersal was assessed in citrus orchards. Furthermore, volatile emission profiles and relative attractiveness of both orange jasmine and sweet orange (Citrus × aurantium L.
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