Development of a PCR-based, genetic marker resource for the tomato-like nightshade relative, Solanum lycopersicoides using whole genome sequence analysis

Screening and identification of functional bacterial attachment genes in aerobic granular sludge

The screening and identification of attachment genes is important to exploring the formation mechanism of biofilms at the gene level. It is helpful to the development of key culture technologies for aerobic granular sludge (AGS). In this study, genome-wide sequencing and gene editing were employed for the first time to investigate the effects and functions of attachment genes in AGS. With the help of whole-genome analysis, ten attachment genes were screened from thirteen genes, and the efficiency of gene screening was greatly improved. Then, two attachment genes were selected as examples to further confirm the gene functions by constructing gene-knockout recombinant mutants of Stenotrophomonas maltophilia; when the two attachment genes were knocked out, the attachment potential was reduced by 50.67% and 43.93%, respectively. The results provide a new theoretical principle and efficient method for the development of AGS from the perspective of attachment genes.

Novel R2R3 MYB transcription factors regulate anthocyanin synthesis in Aubergine tomato plants

BACKGROUND

A high content in anthocyanins, for their health beneficial properties, represents an added value for fruits and vegetables. Tomato (Solanum lycopersicum) is one of the most consumed vegetables worldwide and is rich in vitamins and carotenoids. In recent years, purple-skinned tomatoes, enriched of anthocyanins, were produced recovering allelic variants from wild Solanum species. The molecular basis of the Anthocyanin fruit (Aft) locus, exploited by breeders to activate the anthocyanin synthesis in tomato epicarp, has been recently identified in the correct splicing of the R2R3 MYB gene AN2like. Aubergine (Abg) is a tomato accession which introgressed from Solanum lycopersicoides a locus activating the synthesis of anthocyanins in the fruit. The Abg locus was mapped in the region of chromosome 10 containing Aft and the possibility that Abg and Aft represented alleles of the same gene was hypothesized.

RESULTS

We dissected the R2R3 MYB gene cluster located in the Abg genomic introgression and demonstrated that AN2like is correctly spliced in Abg plants and is expressed in the fruit epicarp. Moreover, its silencing specifically inhibits the anthocyanin synthesis. The Abg allele of AN2like undergoes alternative splicing and produces two proteins with different activities. Furthermore, in Abg the master regulator of the anthocyanin synthesis in tomato vegetative tissues, AN2, is very poorly expressed. Finally, a novel R2R3 MYB gene was identified: it encodes another positive regulator of the pathway, whose activity was lost in tomato and in its closest relatives.

CONCLUSION

In this study, we propose that AN2like is responsible of the anthocyanin production in Abg fruits. Unlike wild type tomato, the Abg allele of AN2like is active and able to regulate its targets. Furthermore, in Abg alternative splicing leads to two forms of AN2like with different activities, likely representing a novel type of regulation of anthocyanin synthesis in tomato.

Alien introgression and morpho-agronomic characterization of diploid progenies of Solanum lycopersicoides monosomic alien addition lines (MAALs) toward pre-breeding applications in tomato (S. lycopersicum)

KEY MESSAGE

Alien introgressions that were captured in the genome of diploid plants segregating from progenies of monosomic alien addition lines of S. lycopersicoides confer novel phenotypes with commercial and agronomic value in tomato breeding. Solanum lycopersicoides is a wild relative of tomato with a natural adaptation to a wide array of biotic and abiotic challenges. In this study, we identified and characterized diploid plants segregating from the progenies of monosomic alien addition lines (MAALs) of S. lycopersicoides to establish their potential as donors in breeding for target trait improvement in tomato. Molecular genotyping identified 28 of 38 MAAL progenies having the complete chromosome complement of the cultivated tomato parent and limited chromosome introgressions from the wild S. lycopersicoides parent. Analysis of SSR and indel marker profiles identified 34 unique alien introgressions in the 28 MAAL-derived introgression lines (MDILs) in the genetic background of tomato. Conserved patterns of alien introgressions were detected among sibs of MDILs 2, 3, 4 and 8. Across MDILs, a degree of preferential transmission of specific chromosome segments was also observed. Morphologically, the MDILs closely resembled the cultivated tomato more than S. lycopersicoides. The appearance of novel phenotypes in the MDILs that are lacking in the cultivated parent or the source MAALs indicates the capture of novel genetic variation by the diploid introgression lines that can add commercial and agronomic value to tomato. In particular, screening of representative MDILs for drought tolerance at the vegetative stage identified MDIL 2 and MDIL 11III as drought tolerant based on visual scoring. A regulated increase in stomatal conductance of MDIL 2 under drought stress indicates better water use efficiency that allowed it to survive for 7 days under 0% moisture level.