Differentially expressed transcripts related to apomixis and ploidy in the diplosporous grass Eragrostis curvula

SELVA JP; PESSINO S; ECHENIQUE V

Wernigerode, Alemania

Congreso; 3rd International Apomixis Conference Wernigerode Germany; 2007

IPK Gatersleben Alemania- Universidad de Perugia Italia

Lovegrasses, Eragrostis curvula (Schrad.) Nees have a basic chromosome number of x = 10. They include a cytotype series with different ploidy levels (from 2x to 8x) and reproductive modes. Although a few sexual diploid (2n = 2x = 20) plants were identified, they are very infrequent (so far only four have been collected) and do not occur in all forms of E. curvula. The more valuable cultivars as forage are tetraploid and apomictic. This mode of reproduction is strongly related to ploidy. Natural and induced polyploidization is in general associated to genetic and epigenetic alterations that affect different genomic regions. The maintaining of homeostasis during this process involved changes in the expression of some genes. The identification of this set of genes will contribute to the elucidation of the molecular basis of diplosporous apomixis in the Gramineae. The objective of this work was to identify mRNA transcripts differentially expressed in flowers and leaves of E. curvula. A tetraploid genotype (T, 4x apo), a sexual diploid derivative obtained from tissue culture (D, 2x sex) and an artificial sexual tetraploid obtained from the diploid seeds after colchicine treatment (C, 4x sex) were used. Differential display assays were conducted on pooled samples by using a mRNA-bulked procedure in order to examine disparity in gene expression between apomictic and sexual plants and between diploid and tetraploid plants. Here we report the isolation and characterization of a family of homologous transcripts presenting differential expression in panicles and leaves of the near isogenic lines of Eragrostis mentioned before. A total of 1100 bands were evaluated from panicles (approximately 50% of the panicle transcriptome). From these bands 181 (16.6%) showed differential expression between plants with different ploidy levels and 13 (1.2%) between plants with different reproductive mode. We observed that both tetraploid plants are more similar between them (97.4% common bands) than each one with the 2x plant (82.1%). These results were very similar when using mRNA extracted from leaves. Until now 70 bands (from differential display using panicles mRNA) were isolated and cloned and 55 were sequenced and characterized. Sequences were queried against GenBank databases using the BLASTX algorithm. Only 18 sequences showed no similarity with any sequence deposited. The other 37 sequences showed similarity with transcription factors, ATPases, kinases, lipid carrier proteins and retrotransposons. Related to ploidy we can mentioned a putative serine carboxypeptidase II, Ubiquitin, retrotransposon protein, H2A protein, zinc finger POZ domain protein-like, ATP binding protein kinase, protein hydroxyproline-rich glycoprotein and leucine aminopeptidase 2. Related to reproductive mode a plasma membrane H+ ATPase was found. At the moment we are sequencing a new set of differential clones and we planned to study the complete transcriptome of weeping lovegrass panicles and leaves. The comparison using both systems, inflorescences and leaves, will allow us to identify transcripts related to reproductive mode and ploidy and to establish, in the near future, the relation between diplospory and ploidy.