Integrative use of comparative omics for harnessing apomixis in plant breeding

COLONO CM; MARINO L; ALTABE S; PODIO M; VEGA MS; VEGA JM; SIENA LA; STEIN J; DELGADO L; ORTIZ JPA; BALABAN D; ACUÑA C; PESSINO SC

Rosario

Congreso; IV International Congress on APOMIXIS; 2023

grupo DREP-IICAR-CONICET

The combined use of sexuality and apomixis (i.e., sexual and asexual reproduction via seeds) in breeding programs allows rapid development of a myriad of improved plant varieties at low cost. The genus Paspalum, one of the best characterized apomictic complexes, includes more than 370 valuable forage species, which were traditionally used in temperate and subtropical regions to feed livestock. The characterization of the molecular control of apomixis in this genus is oriented to: i) the identification of its molecular trigger/s to transfer the trait to major sexual crops, and ii) the harnessing of the trait in Paspalum breeding. Recently, we sequenced the genome of several Paspalum notatum genotypes and identified the genomic region controlling apomixis. Moreover, 454 and Illumina RNAseq analyses were used to spot numerous candidate genes differentially expressed in the reproductive organs of sexual and apomictic plants, some of which map in the genomic region responsible for apomixis. Reverse genetic analyses in model systems revealed that the orthologs of some of these candidates, like TGS1, ARF10 or IAA30, can indeed reproduce apomixis components (i.e., apospory and/or parthenogenesis) in a sexual background, confirming they are suitable candidates to transfer apomixis to sexual crops. Besides, the generation of Paspalum notatum leaf transcriptomes allowed the rapid development of improved apomictic hybrid genotypes. As an example, we will present the development of genotypes with higher content of polyunsaturated fatty acids (PUFAs) using an apomixis-based breeding scheme assisted by molecular markers. Transcript sequences encoding two key proteins of lipid metabolism, SUGAR-DEPENDENT1 (SDP1) and peroxisomal ABC transporter 1 (PXA1), which have been reported to modulate the 18:3 fatty acid content, were recovered from the Paspalum leaf transcriptome. Allele-specific primers were designed and eight representative Paspalum notatum genotypes were screened by qPCR to search for the lower SDP1/PXA1 expression levels. Then, fatty acid methyl esters (FAMEs) gas chromatography was used to analyze the PUFAs representation. We selected a 4x sexual genotype with an optimal molecular profile (i.e., low SDP1/PXA1 expression levels, high content of 18:3) and crossed it with an apomictic pollen donor. Three obligate apomictic genotypes with high content of PUFAs were identified in the F1 family, one of them showing 18:3 values 22,5% ± 1% and 64,2% ± 1% higher than the average of the eight original genotypes and the poorest profiles, respectively. These results show that the use of data derived from comparative omics in Paspalum allows the development of molecular tools for the transference of apomixis into major crops, as well as the assistance of breeding programs to obtain improved cultivars.