Explore the vast range of titles available.

Abstract Following fruit set, the early development of tomato (Lycopersicon esculentum Mill.) fruit comprises two distinct phases: a cell division phase and a consecutive phase of cell expansion until the onset of ripening. In this study, we analyzed cytological and molecular changes characterizing these early phases of tomato fruit development. First we investigated the spatial and temporal regulation of the mitotic activity during fruit development. The DNA content of isolated nuclei from the different fruit tissues was determined by flow cytometry analysis. The results confirm the data of mitotic activity measurements and show that cell differentiation, leading to expanded cells, is characterized by endoreduplication. Second, we isolated two cDNAs, named Lyces;CDKA1 (accession no. Y17225) and Lyces;CDKA2 (accession no. Y17226), encoding tomato homologs of the cyclin-dependent kinase (CDK) p34cdc2. Tomato CDKA gene expression was followed at both the transcriptional and translational levels during fruit development. The transcripts for Lyces;CDKA1 and Lyces;CDKA2 and the corresponding CDKA proteins are predominantly accumulated during the phase of cell division between anthesis and 5 d post anthesis (DPA). In whole fruits, the maximum CDK activity was obtained between 5 and 10 DPA. The determination of the kinase activity using protein extracts from the different fruit tissues was in agreement with mitotic activity analysis. It showed the particular disappearance of the activity in the gel tissue as early as 15 DPA. The overall data of CDK activity measurements suggest a strong post-translational regulation of CDK at the temporal and spatial levels during early tomato fruit development.

Male germline specification is a crucial step in double fertilization in flowering plants. Determining which genes are activated in the male germline, and how those genes are regulated, is essential to understand double fertilization. However, transcription activities in the male germline may be not easy to detect due to low-level expression of some genes and technical difficulties of isolating male germline cells. Here, through a series of gene reporter assays in Arabidopsis, we showed a weak male germline expression pattern of the SOLO DANCERS (SDS) gene, which was confirmed by RT-PCR. Compared to directly fusing the SDS sequence with GFP, adding the coding sequences of other genes such as CDKA1 can greatly enhance the detection of the male germline expression pattern of SDS. We found that SDS expression in the male germline is activated by a novel pathway that differs from the well-known DUO1 regulon. We also developed an SDS-based fluorescence reporter to analyze posttranscriptional regulation in the male germline. Our data suggest that stable gene products of CDKA1 and others may enhance the sensitivity of gene reporters, and the male germline may use diverse pathways to activate gene expression.