Non-additive phenotypic and transcriptomic inheritance in a citrus allotetraploid somatic hybrid between C. reticulata and C. limon: the case of pulp carotenoid biosynthesis pathway (original) (raw)
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Acta horticulturae, 2018
The citrus family (Rutaceae) is a very complex and diverse source of carotenoids. Carotenoid profile and content varies greatly among different species, cultivars and even fruit tissues (e.g., flavedo and juice sacs). In Uruguay, the Citrus Breeding Program is focused on obtaining good quality seedless mandarin cultivars for the fresh market. One of the strategies to improve the nutritional value of citrus, is to increase the accumulation of antioxidant compounds in the fruit pulp. In order to characterize the mechanisms of carotenoid accumulation, we analyzed the carotenoid content in the pulp of five mandarin hybrids through their maturation cycle during the year 2017. Additionally, we analyzed the mRNA expression patterns of key enzymes (PSY, βCHX) of the carotenoid biosynthesis pathway in different maturity stages: immature green (IG), mature green (MG), color break (B), mature (M). Taken together, these results allowed the identification of genotypes that have the potential to accumulate high levels of carotenoids in the pulp and, therefore, are good candidates for genetic engineering of the carotenoid biosynthetic pathway.
Heredity, 2010
Polyploid plants often produce new phenotypes, exceeding the range of variability existing in the diploid gene pool. Several hundred citrus allotetraploid hybrids have been created by somatic hybridization. These genotypes are interesting models to study the immediate effects of allopolyploidization on the regulation of gene expression. Here, we report genome-wide gene expression analysis in fruit pulp of a Citrus interspecific somatic allotetraploid between C. reticulata cv 'Willowleaf mandarin' þ C. limon cv 'Eureka lemon', using a Citrus 20K cDNA microarray. Around 4% transcriptome divergence was observed between the two parental species, and 212 and 160 genes were more highly expressed in C. reticulata and C. limon, respectively. Differential expression of certain genes was confirmed by quantitative real-time RT-PCR. A global downregulation of the allotetraploid hybrid transcriptome was observed, as compared with a theoretical mid parent, for the genes displaying interspecific expression divergence between C. reticulata and C. limon. The genes underexpressed in mandarin, as compared with lemon, were also systematically repressed in the allotetraploid. When genes were overexpressed in C. reticulata compared with C. limon, the distribution of allotetraploid gene expression was far more balanced. Cluster analysis on the basis of gene expression clearly indicated the hybrid was much closer to C. reticulata than to C. limon. These results suggest there is a global dominance of the mandarin transcriptome, in consistence with our previous studies on aromatic compounds and proteomics. Interspecific differentiation of gene expression and non-additive gene regulation involved various biological pathways and different cellular components.
Transcriptional Analysis of Carotenoids Accumulation and Metabolism in a Pink-Fleshed Lemon Mutant
Genes, 2020
Pink lemon is a spontaneous bud mutation of lemon (Citrus limon, L. Burm. f) characterized by the production of pink-fleshed fruits due to an unusual accumulation of lycopene. To elucidate the genetic determinism of the altered pigmentation, comparative carotenoid profiling and transcriptional analysis of both the genes involved in carotenoid precursors and metabolism, and the proteins related to carotenoid-sequestering structures were performed in pink-fleshed lemon and its wild-type. The carotenoid profile of pink lemon pulp is characterized by an increased accumulation of linear carotenoids, such as lycopene, phytoene and phytofluene, from the early stages of development, reaching their maximum in mature green fruits. The distinctive phenotype of pink lemon is associated with an up-regulation and down-regulation of the genes upstream and downstream the lycopene cyclase, respectively. In particular, 9-cis epoxycarotenoid dioxygenase genes were overexpressed in pink lemon compared ...
Journal of Agricultural and Food Chemistry, 2009
The main components of citrus fruit quality (organic acids, sugars, and aromatic compounds) were studied in fruits of a somatic hybrid allotetraploid between Willow leaf mandarin (Citrus deliciosa Ten.) + Eureka lemon [Citrus limon (L.) Burm.] and the two diploid parents. The somatic hybrid (WLM + EUR) combined both nuclear genomes of the parents, with chloroplasts and mitochondria of mandarin. Variations in sugar and acid content were studied in fruit pulp during the maturing period, and the chemical composition of peel oils was investigated by capillary gas chromatography (GC), GC/mass spectrometry (MS), and 13 C NMR. The somatic hybrid was close to the lemon parent in the synthesis of organic acids and close to the mandarin parent in fructose content, while sucrose and glucose contents were between the two parents. The aromatic compounds of WLM + EUR were close to mandarin with a non-negligible effect of lemon, which inhibits the methyl N-methylanthranilate, a mandarin-specific compound. Our results lead us to conclude that biosynthesis of compounds involved in citrus fruit quality is not inherited in an additive way in the allotetraploid hybrid. We observed mandarin dominance for fructose and most of the aromatic compounds, lemon dominance for organic acid and methyl N-methylanthranilate, and codominance for sucrose and glucose.
Carotenoid Biosynthesis and their Regulation in Citrus Fruits
Carotenoids are the main pigments responsible for the attractive color of the peel and pulp of citrus fruits and greatly contribute to their nutritional and antioxidant value. Fruits of different Citrus species display a broad array of color singularities and in many cultivars the peel and the pulp also exhibit different color, envisaging specie-and tissue-specific regulation of the carotenoid content and composition. In addition, citrus mutants affected in fruit color are a useful experimental system to identify molecular mechanisms regulating carotenoid biosynthesis. Citrus is, therefore, an excellent model to study fruit carotenoid accumulation and their regulation. In this review, we summarize and update information on carotenoid content and composition in fruits of agronomically important Citrus species. Current understanding of carotenoids biosynthesis in citrus, highlighting the main regulatory steps of the pathway and how may be related to carotenoid content and complement in peel and pulp of Citrus fruits are discussed. Finally, the effect of environmental and endogenous factors on citrus fruits carotenoids is also evaluated.
Carotenoid Diversity in Cultivated Citrus Is Highly Influenced by Genetic Factors
Journal of Agricultural and Food Chemistry, 2006
Citrus fruits are complex sources of carotenoids with more than 100 kinds of pigments reported in this genus. To understand the origin of the diversity of carotenoid compositions of citrus fruit, 25 genotypes that belong to the 8 cultivated Citrus species were analyzed. Juice extracts of mature fruit were analyzed by high-performance liquid chromatography using a C 30 column. The 25 citrus genotypes presented different carotenoid profiles with 25 distinct compounds isolated. Statistical analyses revealed a strong impact of genotype on carotenoid compositions. Two kinds of classifications of genotypes were performed: on qualitative data and on quantitative data, respectively. The results showed that variability in carotenoid compositions was more interspecific than intraspecific. Two carotenoids, cis-violaxanthin and the-cryptoxanthin, strongly determined the classification on qualitative data, which was also in agreement with previous citrus variety classifications. These findings provide evidence that, as for other phenotypical traits, the general evolution of cultivated Citrus is the main factor of the organization of carotenoid diversity among citrus varieties. To the authors' knowledge this is the first study that links the diversity of carotenoid composition to the citrus genetic diversity. These results lead to the proposed major biosynthetic steps involved in the differential carotenoid accumulation. Possible regulation mechanisms are also discussed.
Flavour and Fragrance Journal, 2005
Leaves of 13 interspecific and intergeneric citrus somatic allotetraploid hybrids were analysed and compared with those of their respective parents (lime, lemons, citron, orange, kumquat, poncirus and mandarin) with regards to their sesquiterpenoid contents (µ µ µ µ µg/g dry weight). The hybrids do not fully retain their parental traits. Sesquiterpenoid production is much reduced (by ~65-90%) in hybrids compared with the sum of their parents. The peculiar behaviours of some compounds were described. Statistical analyses were conducted on a qualitative (the presence/absence of each compound in parents and hybrids) and quantitative (the recovery of each compound in hybrids expressed as a percentage of the sum of its concentration in their parents) basis. Mandarin exerts a strong dominance over its derived hybrids by greatly lowering the production of most compounds, while the expression of parental genomes was more balanced in hybrids having grapefruit or sweet orange as a parent. This decrease in the ability to synthesize sesquiterpenoids could be due to both the tetraploid nature of the hybrids and the dominance of one or other parental genome.
II International Symposium on Citrus Biotechnology, 2011
The survival of the citrus industry is critically dependent on genetically superior cultivars. Improvements in these traits through traditional techniques are unfortunately extremely difficult due to the unusual combination of biological characteristics of citrus. Genomic science holds promise of improvements in breeding and the main goal of our group is to develop genomics tools for the generation of new genotypes. We pursue the identification of candidate genes, alleles and genotypes improving citrus fruit quality and performance, correlating phenotypic analyses, metabolic profiling and gene expression. At completion, genes and alleles with major functions in nutritional quality and stress tolerance could be selected and genotypes with improved fruit composition searched among existing or generated collections. This goal is supported by two complementary strategies the identification of genes of agricultural interest by the use of mutants and microarrays and the elucidation of the citrus genome sequence. In this communication the efforts we are developing in this first approach are revised while the other strategy will be resumed elsewhere. GOALS OF CITRUS BREEDING Major goals of variety breeding in citrus are mostly related to fruit quality, productivity and harvesting period. In a broad sense, citrus fruit quality includes many physical attributes like fruit size, shape, colour, texture, seedlessness, peelability and durability. The chemical characteristics of the fruit, such as sugar and acid content, flavour and aroma compounds (organoleptic properties) are also important. Citrus contain the largest number of carotenoids in addition to an extensive array of secondary compounds with pivotal nutritional properties that greatly contribute to the supply of anticancer agents and other nutraceutical substances essential to prevent cardiovascular and degenerative diseases, thrombosis, cancer, atherosclerosis and obesity. These traits are acquired along fruit growth, from pollination to ripening although they can be strongly modified during post-harvest storage. Extension of the ripening period is also a key target for the market while abscission behaviour plays a major role in fruit production. Citrus Industry basically all over the world is claiming for much more knowledge on the characteristics related to fruit quality. In addition, development of more modern know-how and protocols to generate both phenotypic variability to generate new citrus lines and original procedures for variety authentication are also mayor requirements of the sector. BREEDING PROBLEMS IN CITRUS The reasons for the low impact of traditional breeding of this major fruit crop are related to the peculiarities of citrus reproductive biology (see Talon and Gmitter, 2008). Citrus show apomixy, heterozygosis, facultative parthenocarpy, sterility, and gametophytic self-and cross-incompatibility. In addition to this unusual reproductive biology, Citrus also possess a rare combination of intriguing biological characteristics including non-climacteric fruit ripening, juvenility, dormancy, surprising root/shoot
The Horticulture Journal, 2020
The 'Siam Red Ruby' (Citrus grandis) is a new lycopene-accumulating pumelo variety, which is grown only in the Pakpanang area of the Nakhon Si Thammarat province of Thailand. In this study, we harvested 'Siam Red Ruby' fruit at five ripening stages, and the changes in the accumulation of carotenoid and carotenogenic gene expression were investigated in the pulp. During the ripening process, the contents of phytoene, ζ-Carotene, lycopene, β-carotene, β-cryptoxanthin, and all-trans-violaxanthin increased gradually, while the contents of αcarotene and lutein decreased in the pulp of 'Siam Red Ruby'. In the mature fruit of 'Siam Red Ruby', a high amount of lycopene was accumulated in the pulp, accounting for more than 93.26% of the total carotenoid content. The massive accumulation of lycopene led to an attractive red color of the 'Siam Red Ruby' pulp. In addition, gene expression results showed that the increases in the expression of upstream genes (CitPSY, CitPDS, CitZDS, CitZISO, and CitCRTISO), and decreases in the expression of genes downstream (CitLCYb1, CitLCYb2, CitLCYe, CitHYb, and CitHYe) was the main mechanism of lycopene accumulation in the pulp of 'Siam Red Ruby' pumelo.
Plant molecular …, 2006
Microarrays of cDNA have been used to examine expression changes of 7000 genes during development and ripening of the fruit flesh of selfincompatible Citrus clementina, a non-climateric species. The data indicated that 2243 putative unigenes showed significant expression changes. Functional classification revealed that genes encoding for regulatory proteins were significantly overrepresented in the up-regulated gene clusters. The transcriptomic study together with the analyses of selected metabolites highlighted key physiological processes occurring during citrus fruit development and ripening such as water accumulation, carbohydrate build-up, acid reduction, pigment substitutions (carotenoid accumulation and chlorophyll decreases) and ascorbic acid diminution. Often, the combined analyses strongly suggested prevalence of specific metabolic alternatives. This observation has been exemplified with the