expanded tomato fruit volatile landscape Rambla, José L; Tikunov, Yury M; Monforte, Antonio J ...
Journal of experimental botany,
08/2014, Letnik:
65, Številka:
16
Journal Article
Recenzirano
Odprti dostop
A tomato fruit volatile review is presented which addresses updated biosynthesis pathways, control of emission by conjugation and hydrolysis, and discussion about the difficulties in and ...opportunities for breeding better tasting tomatoes.
Tomato (Solanum lycopersicum) contains two close homologs of the Arabidopsis thaliana MADS domain transcription factor FRUITFULL (FUL), FUL1 (previously called TDR4) and FUL2 (previously MBP7). Both ...proteins interact with the ripening regulator RIPENING INHIBITOR (RIN) and are expressed during fruit ripening. To elucidate their function in tomato, we characterized single and double FUL1 and FUL2 knockdown lines. Whereas the single lines only showed very mild alterations in fruit pigmentation, the double silenced lines exhibited an orange-ripe fruit phenotype due to highly reduced lycopene levels, suggesting that FUL1 and FUL2 have a redundant function in fruit ripening. More detailed analyses of the phenotype, transcriptome, and metabolome of the fruits silenced for both FUL1 and FUL2 suggest that the genes are involved in cell wall modification, the production of cuticle components and volatiles, and glutamic acid (Glu) accumulation. Glu is responsible for the characteristic umami taste of the present-day cultivated tomato fruit. In contrast with previously identified ripening regulators, FUL1 and FUL2 do not regulate ethylene biosynthesis but influence ripening in an ethylene-independent manner. Our data combined with those of others suggest that FUL1/2 and TOMATO AGAMOUS-LIKE1 regulate different subsets of the known RIN targets, probably in a protein complex with the latter.
Among the abiotic stresses affecting plant reproduction, high temperature is one of the most prominent ones because it directly affects fruit set. So far, little attention has been paid to the ...investigation of the variation in high temperature tolerance among wild tomato (
Solanum lycopersicum)
germplasm. The objective of this study was to determine the tolerance of 17 different cultivated and wild tomato accessions to high temperature, using a pollen viability screening approach. Each of the 17 genotypes of tomato was analysed for their pollen quality under a 32 °C (day)/26 °C (night) regime. The total number of pollen per flower and the fraction of viable pollen were recorded. The number of pollen per flower varied between 35,547 and 109,490 whereas the fraction of viable pollen varied between 0.03 and 0.71. No correlation was found between these two traits. However, the combination of these traits could provide the best reproductive capability under high temperature. In this study, thermo-tolerant (LA2854, LA1478 and LA0417) as well as thermo-sensitive (LA1719, LA1580, and SWEET4) genotypes have been identified. Those genotypes can be used as novel genetic resources to get more insight into pollen thermo-tolerance mechanisms and be included in breeding programs.
The transformation of the ovary into a fruit after successful completion of pollination and fertilization has been associated with many changes at transcriptomic level. These changes are part of a ...dynamic and complex regulatory network that is controlled by phytohormones, with a major role for auxin. One of the auxin-related genes differentially expressed upon fruit set and early fruit development in tomato is Solanum lycopersicum AUXIN RESPONSE FACTOR 9 (SlARF9). Here, the functional analysis of this ARF is described. SlARF9 expression was found to be auxin-responsive and SlARF9 mRNA levels were high in the ovules, placenta, and pericarp of pollinated ovaries, but also in other plant tissues with high cell division activity, such as the axillary meristems and root meristems. Transgenic plants with increased SlARF9 mRNA levels formed fruits that were smaller than wild-type fruits because of reduced cell division activity, whereas transgenic lines in which SlARF9 mRNA levels were reduced showed the opposite phenotype. The expression analysis, together with the phenotype of the transgenic lines, suggests that, in tomato, ARF9 negatively controls cell division during early fruit development.
Parthenocarpy, the formation of seedless fruits in the absence of functional fertilization, is a desirable trait for several important crop plants, including tomato (Solanum lycopersicum). Seedless ...fruits can be of great value for consumers, the processing industry, and breeding companies. In this article, we propose a novel strategy to obtain parthenocarpic tomatoes by down-regulation of the flavonoid biosynthesis pathway using RNA interference (RNAi)-mediated suppression of chalcone synthase (CHS), the first gene in the flavonoid pathway. In CHS RNAi plants, total flavonoid levels, transcript levels of both Chs1 and Chs2, as well as CHS enzyme activity were reduced by up to a few percent of the corresponding wild-type values. Surprisingly, all strong Chs-silenced tomato lines developed parthenocarpic fruits. Although a relation between flavonoids and parthenocarpic fruit development has never been described, it is well known that flavonoids are essential for pollen development and pollen tube growth and, hence, play an essential role in plant reproduction. The observed parthenocarpic fruit development appeared to be pollination dependent, and Chs RNAi fruits displayed impaired pollen tube growth. Our results lead to novel insight in the mechanisms underlying parthenocarpic fruit development. The potential of this technology for applications in plant breeding and biotechnology will be discussed.
Phenylpropanoid volatiles are responsible for the key tomato fruit (Solanum lycopersicum) aroma attribute termed "smoky." Release of these volatiles from their glycosylated precursors, rather than ...their biosynthesis, is the major determinant of smoky aroma in cultivated tomato. Using a combinatorial omics approach, we identified the NON-SMOKY GLYCOSYLTRANSFERASE1 (NSGT1) gene. Expression of NSGT1 is induced during fruit ripening, and the encoded enzyme converts the cleavable diglycosides of the smoky-related phenylpropanoid volatiles into noncleavable triglycosides, thereby preventing their deglycosylation and release from tomato fruit upon tissue disruption. In an nsgt1/nsgt1 background, further glycosylation of phenylpropanoid volatile diglycosides does not occur, thereby enabling their cleavage and the release of corresponding volatiles. Using reverse genetics approaches, the NSGT1-mediated glycosylation was shown to be the molecular mechanism underlying the major quantitative trait locus for smoky aroma. Sensory trials with transgenic fruits, in which the inactive nsgt1 was complemented with the functional NSGT1, showed a significant and perceivable reduction in smoky aroma. NSGT1 may be used in a precision breeding strategy toward development of tomato fruits with distinct flavor phenotypes.
Plants with innate disease and pest resistance can contribute to more sustainable agriculture. Natural defence compounds produced by plants have the potential to provide a general protective effect ...against pathogens and pests, but they are not a primary target in resistance breeding. Here, we identified a wild relative of potato,
Solanum commersonii
, that provides us with unique insight in the role of glycoalkaloids in plant immunity. We cloned two atypical resistance genes that provide resistance to
Alternaria solani
and Colorado potato beetle through the production of tetraose steroidal glycoalkaloids (SGA). Moreover, we provide in vitro evidence to show that these compounds have potential against a range of different (potato pathogenic) fungi. This research links structural variation in SGAs to resistance against potato diseases and pests. Further research on the biosynthesis of plant defence compounds in different tissues, their toxicity, and the mechanisms for detoxification, can aid the effective use of such compounds to improve sustainability of our food production.
Farmers often rely on pesticides to protect their crops from disease and pests. However, these chemicals are harmful to the environment and more sustainable strategies are needed. This is particularly true for a disease known as the early blight of potato, which is primarily treated using fungicides that stop the fungal pathogen responsible for the infection (
Alternaria solani
) from growing.
An alternative approach is to harness the natural defence systems that plants already have in place to protect themselves. Like humans, plants have an immune system which can detect and destroy specific pathogens. On top of this, they release defence compounds that are generally toxic to pests and microbes, stopping them from infiltrating and causing an infection.
In 2021, a group of researchers discovered a wild relative of the potato, known as
Solanum commersonii,
with strong resistance to early blight disease. Here, Wolters et al. – including some of the researchers involved in the 2021 study – set out to find how this plant defends itself from the fungus
A
.
solani
.
The team found that two closely linked genes are responsible for the resistant behaviour of
S. commersonii,
which both encode enzymes known as glycosyltransferases. Further experiments revealed that the enzymes protect
S. commersonii
from early blight disease by modifying steroidal glycoalkaloids, typical defence compounds found in potato and other plants from the same family. The glycosyltransferases alter glycoalkaloids in
S. commersonii
by adding a sugar group to a specific part of the compound called glycone.
Wolters et al. found that the glycoalkaloids from
S. commersonii
were able to slow the growth of other fungal pathogens that harm potatoes when tested in the laboratory. They also made plants resistant to another common destroyer of crops, the Colorado potato beetle.
These findings could help farmers breed potatoes and other crops that are more resistant to early blight disease and Colorado potato beetle, as well as potentially other fungi and pests. However, further experiments are needed to investigate how these glycone-modified glycoalkaloids affect humans, and how variants of glycoalkaloids are produced and degraded in different parts of the plants. Acquiring this knowledge will help to employ these defence compounds in a safe and effective manner.
SUMMARY
Tomato (Solanum lycopersicum L.) has become a popular model for genetic studies of fruit flavor in the last two decades. In this article we present a study of tomato fruit flavor, including ...an analysis of the genetic, metabolic and sensorial variation of a collection of contemporary commercial glasshouse tomato cultivars, followed by a validation of the associations found by quantitative trait locus (QTL) analysis of representative biparental segregating populations. This led to the identification of the major sensorial and chemical components determining fruit flavor variation and detection of the underlying QTLs. The high representation of QTL haplotypes in the breeders’ germplasm suggests that there is great potential for applying these QTLs in current breeding programs aimed at improving tomato flavor. A QTL on chromosome 4 was found to affect the levels of the phenylalanine‐derived volatiles (PHEVs) 2‐phenylethanol, phenylacetaldehyde and 1‐nitro‐2‐phenylethane. Fruits of near‐isogenic lines contrasting for this locus and in the composition of PHEVs significantly differed in the perception of fruity and rose‐hip‐like aroma. The PHEV locus was fine mapped, which allowed for the identification of FLORAL4 as a candidate gene for PHEV regulation. Using a gene‐editing‐based (CRISPR‐CAS9) reverse‐genetics approach, FLORAL4 was demonstrated to be the key factor in this QTL affecting PHEV accumulation in tomato fruit.
Significance Statement
In commercial tomato breeding, elite breeding lines remain the major source of new cultivars. We studied the sensorial, chemical and genetic components of fruit flavor in a collection of commercial glasshouse tomatoes. The haplotypes associated with the flavor QTLs characterized in this study were well represented in the current breeders’ germplasm. Fine mapping of the major QTLs for floral phenolic volatiles resulted in the identification and functional confirmation of the causal gene.
•Spoilage rates of grey mold disease differed between strawberry genotypes.•Red color intensity of the fruit skin correlated to lower spoilage rates.•Higher levels of ethyl butanoate and 1-hexanol ...correlated to higher spoilage rates.•Anthocyanin and ascorbic acid levels were not correlated to spoilage rates.•Fruit sugar levels were not correlated to spoilage rates.
The relations between physical and chemical characteristics (e.g., color, firmness, volatile and non-volatile metabolites) of red ripe strawberry fruit and the natural spoilage caused by Botrytis cinerea were investigated. The spoilage rates differed between genotypes, and this was highly correlated over two successive years. Among seventeen genotypes, a more intense red coloration of the fruit skin was associated with a lower spoilage rate (r = –0.63). Additionally, weakly negative correlations were found between the levels of anthocyanins, ascorbic acid, malic acid and spoilage rates. No clear correlations were found between spoilage rates and soluble sugars, most volatiles, firmness and dry weight percentage. High levels of two volatile compounds, ethyl butanoate (r = 0.55) and 1-hexanol (r = 0.61), were correlated to high spoilage rates. These characteristics may assist strawberry breeders in selecting for genotypes with reduced susceptibility to B. cinerea.
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