Plant & Animal Genomes XIII Conference

January 15-19, 2005
Town & Country Convention Center
San Diego, CA

Plant Genomes Contain Mob1-Like Gene Family Members That Are Specifically Expresed In Reproductive Tissues And Their Producs Correlate With Either Apomeiosis Or Programmed Cell Death

Sandra Citterio¹ , Serena Varotto ² , Emidio Albertini³ , Margherita Lucchin² , Barcaccia Gianni²

¹  Dipartimento di Scienze dell’Ambiente e del Territorio, University of Milano – Bicocca, Piazza della Scienza 1, 20126 Milano, Italy;

²  Dipartimento di Agronomia Ambientale e Produzioni Vegetali, University of Padova, Agripolis, Via dell’Università 16, 35020 Legnaro, Padova, Italy;

³  Dipartimento di Biologia Vegetale e Biotecnologie Agroambientali, University of Perugia, Borgo XX Giugno 74, 06121 Perugia, Italy

Plant genomes appear, like yeast and human genomes, to contain two types of Mob-like genes. An EST with significant similarity to the Mob1 gene family members was isolated by mRNA profiling in flower buds of the reproductive mutant TWO-N-EGG of Medicago sativa. A set of cDNA full-lengths was obtained by RACE and characterized to contain two distinct Mob1-like ORFs. RT-PCR analysis proved that one member is expressed only in flower buds during sporogenesis, differentially between mutant and wild-type, whereas the other is constitutively expressed in both genotypes. A doublet of proteins of 28 and 47 kDa was visualized by a polyclonal antibody in rootlet and cotyledon isolates, providing that Mob1 may be a component of multi-domain proteins. In the mutant, in situ hybridization revealed two antisense patterns for the Mob1-like genes: one in degenerating megaspores of ovules undergoing regular meiosis and the other in enlarged MMCs and embryo sacs of apomeiotic ovules. The signal was also expressed in tapetal cells of anthers naturally undergoing PCD. Similar distribution patterns in ovules and anthers were also visualized for Mob1-like proteins through immuno-localization. TUNEL analysis showed that both transcript and protein localization signals within reproductive tissues spatially and temporarily overlap sites characterized by DNA fragmentation. Overall results were consistent with the concept that Mob1-like gene products are associated with the fate of megaspores in the ovules. We are presently carrying out studies in Arabidopsis thaliana and Petunia hybrida to ascertain whether Mob1-like proteins function during mitotic and meiotic spindle assembly and activity.