The role of strigolactones in P deficiency induced transcriptional changes in tomato roots

BACKGROUND: Phosphorus (P) is an essential macronutrient for plant growth and development. Upon P shortage, plant responds with massive reprogramming of transcription, the Phosphate Starvation Response (PSR). In parallel, the production of strigolactones (SLs)—a class of plant hormones that regulates plant development and rhizosphere signaling molecules—increases. It is unclear, however, what the functional link is between these two processes. In this study, using tomato as a model, RNAseq was used to evaluate the time-resolved changes in gene expression in the roots upon P starvation and, using a tomato CAROTENOID CLEAVAGE DIOXYGENASES 8 (CCD8) RNAi line, what the role of SLs is in this. RESULTS: Gene ontology (GO)-term enrichment and KEGG analysis of the genes regulated by P starvation and P replenishment revealed that metabolism is an important component of the P starvation response that is aimed at P homeostasis, with large changes occurring in glyco-and galactolipid and carbohydrate metabolism, biosynthesis of secondary metabolites, including terpenoids and polyketides, glycan biosynthesis and metabolism, and amino acid metabolism. In the CCD8 RNAi line about 96% of the PSR genes was less affected than in wild-type (WT) tomato. For example, phospholipid biosynthesis was suppressed by P starvation, while the degradation of phospholipids and biosynthesis of substitute lipids such as sulfolipids and galactolipids were induced by P starvation. Around two thirds of the corresponding transcriptional changes depend on the presence of SLs. Other biosynthesis pathways are also reprogrammed under P starvation, such as phenylpropanoid and carotenoid biosynthesis, pantothenate and CoA, lysine and alkaloids, and this also partially depends on SLs. Additionally, some plant hormone biosynthetic pathways were affected by P starvation and also here, SLs are required for many of the changes (more than two thirds for Gibberellins and around one third for Abscisic acid) in the gene expression. CONCLUSIONS: Our analysis shows that SLs are not just the end product of the PSR in plants (the signals secreted by plants into the rhizosphere), but also play a major role in the regulation of the PSR (as plant hormone). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12870-021-03124-0

Identification of microRNA targets in tomato fruit development using high-throughput sequencing and degradome analysis

By using parallel analysis of RNA ends (PARE) for global identification of miRNA targets and comparing four different stages of tomato fruit development we identified a large number of target genes of miRNAs. PARE libraries were produced, one each, for tomato fruits at 5 days after pollination, mature green fruit, Breaker fruit, and 7 days after Breaker stge fruit

Identification of microRNA targets in tomato fruit development using high-throughput sequencing and degradome analysis

MicroRNAs (miRNAs) play important roles in plant development through regulation of gene expression by mRNA degradation or translational inhibition. Despite the fact that tomato (Solanum lycopersicum) is the model system for studying fleshy fruit development and ripening, only a few experimentally proven miRNA targets are known, and the role of miRNA action in these processes remains largely unknown. Here, by using parallel analysis of RNA ends (PARE) for global identification of miRNA targets and comparing four different stages of tomato fruit development, a total of 119 target genes of miRNAs were identified. Of these, 106 appeared to be new targets. A large part of the identified targets (56) coded for transcription factors. Auxin response factors, as well as two known ripening regulators, COLORLESS NON-RIPENING (CNR) and APETALA2a (SlAP2a), with developmentally regulated degradation patterns were identified. The levels of the intact messenger of both CNR and AP2a are actively modulated during ripening, by miR156/157 and miR172, respectively. Additionally, two TAS3-mRNA loci were identified as targets of miR390. Other targets such as ARGONAUTE 1 (AGO1), shown to be involved in miRNA biogenesis in other plant species, were identified, which suggests a feedback loop regulation of this process. In this study, it is shown that miRNA-guided cleavage of mRNAs is likely to play an important role in tomato fruit development and ripenin

Identification of microRNA targets in tomato fruit development using high-throughput sequencing and degradome analysis

MicroRNAs (miRNAs) play important roles in plant development through regulation of gene expression by mRNA degradation or translational inhibition. Despite the fact that tomato (Solanum lycopersicum) is the model system for studying fleshy fruit development and ripening, only a few experimentally proven miRNA targets are known, and the role of miRNA action in these processes remains largely unknown. Here, by using parallel analysis of RNA ends (PARE) for global identification of miRNA targets and comparing four different stages of tomato fruit development, a total of 119 target genes of miRNAs were identified. Of these, 106 appeared to be new targets. A large part of the identified targets (56) coded for transcription factors. Auxin response factors, as well as two known ripening regulators, COLORLESS NON-RIPENING (CNR) and APETALA2a (SlAP2a), with developmentally regulated degradation patterns were identified. The levels of the intact messenger of both CNR and AP2a are actively modulated during ripening, by miR156/157 and miR172, respectively. Additionally, two TAS3-mRNA loci were identified as targets of miR390. Other targets such as ARGONAUTE 1 (AGO1), shown to be involved in miRNA biogenesis in other plant species, were identified, which suggests a feedback loop regulation of this process. In this study, it is shown that miRNA-guided cleavage of mRNAs is likely to play an important role in tomato fruit development and ripenin

Solanum lycopersicum cv. Heinz 1706 chromosome 6: distribution and abundance of genes and retrotransposable elements

We studied the physical and genetic organization of chromosome 6 of tomato (Solanum lycopersicum) cv. Heinz 1706 by combining bacterial artificial chromosome (BAC) sequence analysis, high-information-content fingerprinting, genetic analysis, and BAC-fluorescent in situ hybridization (FISH) mapping data. The chromosome positions of 81 anchored seed and extension BACs corresponded in most cases with the linear marker order on the high-density EXPEN 2000 linkage map. We assembled 25 BAC contigs and eight singleton BACs spanning 2.0 Mb of the short-arm euchromatin, 1.8 Mb of the pericentromeric heterochromatin and 6.9 Mb of the long-arm euchromatin. Sequence data were combined with their corresponding genetic and pachytene chromosome positions into an integrated map that covers approximately a third of the chromosome 6 euchromatin and a small part of the pericentromeric heterochromatin. We then compared physical length (Mb), genetic (cM) and chromosome distances (¿m) for determining gap sizes between contigs, revealing relative hot and cold spots of recombination. Through sequence annotation we identified several clusters of functionally related genes and an uneven distribution of both gene and repeat sequences between heterochromatin and euchromatin domains. Although a greater number of the non-transposon genes were located in the euchromatin, the highly repetitive (22.4%) pericentromeric heterochromatin displayed an unexpectedly high gene content of one gene per 36.7 kb. Surprisingly, the short-arm euchromatin was relatively rich in repeats as well, with a repeat content of 13.4%, yet the ratio of Ty3/Gypsy and Ty1/Copia retrotransposable elements across the chromosome clearly distinguished euchromatin (2:3) from heterochromatin (3:2

Solanum lycopersicum cv. Heinz 1706 chromosome 6: distribution and abundance of genes and retrotransposable elements

We studied the physical and genetic organization of chromosome 6 of tomato (Solanum lycopersicum) cv. Heinz 1706 by combining bacterial artificial chromosome (BAC) sequence analysis, high-information-content fingerprinting, genetic analysis, and BAC-fluorescent in situ hybridization (FISH) mapping data. The chromosome positions of 81 anchored seed and extension BACs corresponded in most cases with the linear marker order on the high-density EXPEN 2000 linkage map. We assembled 25 BAC contigs and eight singleton BACs spanning 2.0 Mb of the short-arm euchromatin, 1.8 Mb of the pericentromeric heterochromatin and 6.9 Mb of the long-arm euchromatin. Sequence data were combined with their corresponding genetic and pachytene chromosome positions into an integrated map that covers approximately a third of the chromosome 6 euchromatin and a small part of the pericentromeric heterochromatin. We then compared physical length (Mb), genetic (cM) and chromosome distances (¿m) for determining gap sizes between contigs, revealing relative hot and cold spots of recombination. Through sequence annotation we identified several clusters of functionally related genes and an uneven distribution of both gene and repeat sequences between heterochromatin and euchromatin domains. Although a greater number of the non-transposon genes were located in the euchromatin, the highly repetitive (22.4%) pericentromeric heterochromatin displayed an unexpectedly high gene content of one gene per 36.7 kb. Surprisingly, the short-arm euchromatin was relatively rich in repeats as well, with a repeat content of 13.4%, yet the ratio of Ty3/Gypsy and Ty1/Copia retrotransposable elements across the chromosome clearly distinguished euchromatin (2:3) from heterochromatin (3:2

The genome of Gynandropsis gynandra provides insights into whole-genome duplications and the evolution of C4 photosynthesis in Cleomaceae

Gynandropsis gynandra (Cleomaceae) is a cosmopolitan leafy vegetable and medicinal plant, which has also been used as a model to study C4 photosynthesis due to its evolutionary proximity to Arabidopsis. Here, we present a high-quality genome sequence of G. gynandra, anchored onto 17 main super- scaffolds with a total length of 740 Mb, an N50 of 42 Mb and 30,933 well-supported gene models. The G. gynandra genome and previously released genomes of C3 relatives in the Cleomaceae and Brassicaceae make an excellent model for studying the role of genome evolution in the transition from C3 to C4 photosynthesis. We revealed that G. gynandra and its C3 relative Tarenaya hassleriana shared a whole-genome duplication event (Gg-α), then an addition of a third genome (Th-α, +1x) took place in T. hassleriana but not in G. gynandra. Analysis of syntenic copy number of C4 photosynthesis-related gene families indicates that G. gynandra generally retained more duplicated copies of these genes than C3 T. hassleriana, and also that the G. gynandra C4 genes might have been under positive selection pressure. Both whole-genome and single-gene duplication were found to contribute to the expansion of the aforementioned gene families in G. gynandra. Collectively, this study enhances our understanding of the impact of gene duplication and gene retention on the evolution of C4 photosynthesis in Cleomaceae