Identification of genes related to endosperm balance number insensitivity during seed setting in Paspalum notatum Flüggé

DEPETRIS, MARA B.; ACUÑA, C.A.; QUARIN, C.; FELITTI, S.A.

Buenos Aires

Simposio; 5th International Symposium of Forage Breeding.; 2015

Facultad de Agronomía, Universidad de Buenos Aires

The theory of endosperm balance number (EBN) postulates that each species has an effective number that is important for normal endosperm and seed development to occur. However, the endosperm formation in apomictic P. notatum does not depend on it for setting seed. The aim of this work was to characterize the transcriptome during seed formation in apomictic and sexual plants using cDNA-AFLP methodology. Crosses were made in order to induce the development of seeds with different maternal/paternal (m:p) genomic ratios in the endosperm. Previous information indicated that pollen grains germinated on stigma papillae about 15 min after pollination and pollen tubes spent 90?150 min reaching and penetrating the ovule through the micropile. In order to detect differences during the early formation seeds, RNA was isolated from ovaries 3 h after pollination allowing fertilization to succeed. As low fertility is given by a post-zygotic abortion, analysis at 24 h was also carried out, when endosperm growth rate was expected to be at its maximum level and before the endosperm collapse. The results showed that 46 of the 100 differentially expressed transcript-derived fragments (DETDFs) were specifically found in ovaries from apomictic plants with EBN different to 2:1, 3 h after pollination. Out of those, 12 had high identity with proteins expressed in response to changes in the levels of extracellular ATP (eATP) in Arabidopsis. It suggest that eATP-mediated signaling could be involved in the regulation of endosperm development. After 24 h, a DETDF isolated from apomicitic ovaries was predicted to be involved in sucrose metabolism during the massive accumulation of hexose and starch in the endosperm and might be related to EBN insensitivity. In sexual ovaries where the EBN was different 2:1 (no seed expected), a DETDF was similar to a gene associated to the failure of fusion of the polar nuclei during megagametogenesis, while others 3 presented high similarity with a Calcium-dependent Protein Kinase that regulates the accumulation of storage products in immature seed of A. thaliana. Both might be involved in the failure of endosperm development. These results will help us to understand the mechanism by which this system produces seeds regardless of the strict ratio (2m: 1p) present in most grass species.