Identification of genes related to endosperm balance number insensitivity in Paspalum notatum

Abstract

The endosperm balance number (EBN) theory states that genomic contribution ratio should be kept at 2:1 maternal/paternal (m:p) ratio for normal endosperm development. However, the endosperm formation in apomictic Paspalum notatum Flüggé does not depend on the EBN. The aim of this work was to characterize gene expression during seed formation from apomictic and sexual P. notatum using complementary DNA-amplified fragment length polymorphism methodology. To induce the formation of seeds with different m:p genomic ratios, crosses were made between genotypes with different ploidy levels and reproductive modes. RNA was isolated from ovaries 24 h after pollination, when maximum endosperm growth rate was expected. Some of the 49 differen-tially expressed transcript-derived fragments (DETDFs) provided relevant information. Three of those were found in ovaries of apomictic plants with an EBN different from 2:1. A DETDF was predicted to be involved in sucrose metabolism during the accumulation of hexose and starch in the endosperm and might be related to EBN insensitivity. Twenty-two DETDFs were found in crosses where sexual plants were used as the female parent and the predicted m:p ratio was not 2:1. One of those was related to the failure of fusion of the polar nuclei in Arabidopsis thaliana (L.) Heynh. Finally, three transcripts presented similarity with a casein kinase II that regulates the accumulation of storage products in seeds of A. thaliana. Both processes might be involved in endosperm development in P. notatum.