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†Background and Aims Hourglass cells (HGCs) are prominent cells in the soybean seed coat, and have potentialuse as ‘phytofactories’ to produce specific proteins of interest. Previous studies have shown that HGCs initiatedifferentiation at about 9 d post-anthesis (dpa), assuming their characteristic morphology by 18 dpa. Thisstudy aims to document the structural changes in HGCs during this critical period, and to relate these changesto the concurrent development of a specific soybean peroxidase (SBP) encoded by the Ep gene.†Methods Pods were collected from plants at specific growth stages. Fresh material was processed for analysis ofEp peroxidase activity. Tissues were processed for scanning and transmission electron microscopy, as well asextracted for western blotting. A null variety lacking expression of Ep peroxidase was grown as a control.†Key Results and Conclusions At 9 dpa, HGCs are typical undifferentiated plant cells, but from 12–18 dpa theyundergo rapid changes in their internal and external structure. By 18 dpa, they have assumed the characteristichourglass shape with thick cell walls, intercellular air spaces and large central vacuoles. By 45 dpa, all organellesin HGCs have been degraded. Additional observations indicate that plasmodesmata connect all cell types. SBPactivity and SBP protein are detectable in the HGC before they are fully differentiated (approx. 18 dpa). In veryearly stages, SBP activity appears localized in a vacuole as previously predicted. These results increase our under-standing of the structure and development of the HGC and will be valuable for future studies aimed at proteintargeting to components of the HGC endomembrane systems.Key words: Glycine max, soybean, seed coat, hourglass cells, development, peroxidase.

The regulation of ACC synthase (ACS) genes was studied in early (‘Early Golden’) and late (‘Shiro’) Japanese plum cultivars (Prunus salicina L.) in order to determine the role of this gene family in fruit ripening. Of the four Ps-ACS cDNAs isolated, two (Ps-ACS1 and -3) showed differential expression between the two cultivars. Ps-ACS1 accumulated during fruit ripening of ‘Early Golden’ (‘EG’) and ‘Shiro’ (‘SH’) in ethylene-dependent and -independent manners, respectively. Ps-ACS3a transcripts accumulated throughout fruit development and during ‘EG’ fruit ripening. Ps-ACS3b was detected only during ripening of ‘SH’ fruit. Furthermore, Ps-ACS3a transcript accumulation was negatively regulated by ethylene, whereas Ps-ACS3b was positively induced by the hormone. In both cultivars, the expression of Ps-ACS4 and -5 is under positive and negative feedback control by ethylene, respectively. Genetic analyses of ‘EG’ and ‘SH’ cultivars demonstrated that ‘EG’ is homozygous for Ps-ACS3a whereas ‘SH’ is heterozygous for Ps-ACS3 (a/b). The role of ethylene-overproducer 1-like in delaying fruit ripening by interacting with Ps-ACS proteins was also studied. The effect of the plant hormones, auxin, gibberellin, and cytokinin, in regulating ethylene production by promoting the induction of the different Ps-ACS mRNAs in plum was investigated. A model is presented in which differences in Ps-ACS alleles and gene expression between early and late plums are critical in determining the ripening behaviour of the cultivars.