Jingmei Liu

Two negative cis-regulatory regions involved in fruit-specific promoter activity from watermelon (Citrullus vulgaris S.)

A 1.8 kb 5′-flanking region of the large subunit of ADP-glucose pyrophosphorylase, isolated from watermelon (Citrullus vulgaris S.), has fruit-specific promoter activity in transgenic tomato plants. Two negative regulatory regions, from –986 to –959 and from –472 to –424, were identified in this promoter region by fine deletion analyses. Removal of both regions led to constitutive expression in epidermal cells. Gain-of-function experiments showed that these two regions were sufficient to inhibit RFP (red fluorescent protein) expression in transformed epidermal cells when fused to the cauliflower mosaic virus (CaMV) 35S minimal promoter. Gel mobility shift experiments demonstrated the presence of leaf nuclear factors that interact with these two elements. A TCCAAAA motif was identified in these two regions, as well as one in the reverse orientation, which was confirmed to be a novel specific cis-element. A quantitative β-glucuronidase (GUS) activity assay of stable transgenic tomato plants showed that the activities of chimeric promoters harbouring only one of the two cis-elements, or both, were ∼10-fold higher in fruits than in leaves. These data confirm that the TCCAAAA motif functions as a fruit-specific element by inhibiting gene expression in leaves.

Regeneration of Lo Han Kuo (Siraitia grosvenori) in vitro by Direct Organogenesis

Abstract The traditional technique for asexual propagation of Siraitia grosvenori in vitro is adopted widely by pressing the vine, which has a high risk of carrying viral diseases and limits the production of promoted cultivars. So this paper reported in vitro regeneration of S. grosvenori by testing for shoot induction from various explant sources such as leaf, petiole and stem. Several phytohormone combinations of TDZ, BA and IAA were examined for shoot regeneration and NAA or IBA for rooting. The highest shoot induction rate (100% of regeneration frequency and 15.3 shoots per explant) in leaf was obtained by incubation on MS medium supplemented with 0.5 mg · L−1 TDZ, 2.0 mg · L−1 BA and 0.5 mg · L−1 IAA; unlike shoot regeneration in leaves, the most efficient bud inductions in petiole and stem explants were initiated on MS medium containing 0.2 mg · L−1 TDZ, 2.0 mg · L−1 BA and 0.5 mg · L−1 IAA, in addition, adventitious buds in petiole and stem explants needed to be transformed to MS medium for development; optimal root was obtained when shoots were cultured on 1/2MS medum supplemented with 0.5 mg · L−1 NAA or 0.5 mg · L−1 IBA.