Octoploid strawberry (Fragaria x ananassa Duch.) is a model plant for research and one of the most important non-climacteric fruit crops throughout the world. The associations between regulatory networks and metabolite composition were explored for one of the most critical agricultural properties in octoploid strawberry, fruit colour. Differences in the levels of flavonoids are due to the differences in the expression of structural and regulatory genes involved in flavonoid biosynthesis. The molecular mechanisms underlying differences in fruit colour were compared between red and white octoploid strawberry varieties. FaMYB genes had combinatorial effects in determining the red colour of fruit through the regulation of flavonoid biosynthesis in response to the increase in endogenous ABA at the final stage of fruit development. Analysis of alleles of FaMYB10 and FaMYB1 in red and white strawberry varieties led to the discovery of a white-specific variant allele of FaMYB10, FaMYB10-2. Its coding sequence possessed an ACTTATAC insertion in the genomic region encoding the C-terminus of the protein. This insertion introduced a predicted premature termination codon, which suggested the loss of intact FaMYB10 protein playing a critical role in the loss of red colour in white octoploid strawberry.

Two plasmids, p13GUS and p13GUS2, were constructed to create a gene trap system containing the promoterless beta-glucuronidase (GUS) reporter gene in the T-DNA region. Transformation of these two plasmids into the rice variety Zhonghua 11 (Oryza sativa ssp. japonica cv.), mediated by Agrobacterium tumefaciens, resulted in 942 independent transgenic lines. Histochemical GUS assays revealed that 31 T(0) plants had various patterns of the reporter gene expression, including expression in only one tissue, and simultaneously in two or more tissues. Hygromycin-resistant (hyg(r)) homozygotes were screened and the copy number of the T-DNA inserts was determined in the GUS-positive transgenic plants. The flanking sequences of the T-DNA were isolated by inverse-polymerase chain reaction and the insert positions on the rice genome of T-DNA were determined by a basic local alignment search tool in the GUS-positive transgenic plants transformed with plasmid p13GUS. Moreover, calli induced from the seeds of the T(1) generation of 911 GUS-negative transgenic lines were subjected to stress and hormone treatments. Histochemical GUS assays were carried out on the calli before and after treatment. The results revealed that calli from 21 lines displayed differential GUS expression after treatment. All of these data demonstrated that this trap system is suitable for identifying rice genes, including those that are sensitive to induction.

The coding region of Bar gene, the left border of Ds element, the coding region of GUS gene, the transposase of Ac element, the right border of Ds element and the promoter of Ubi gene were inserted into the T-DNA region of vector pCAMBIA1300 in turn to construct plasmid p13B. The orientations of the ubiquitons' promoter, Ac transposase and Bar are identical but opposite to that of the GUS gene (Fig.1). The plasmid p13B was then introduced into the calli of Oryza sativa subsp. japonica cv. Zhonghua 11 by Agrobacterium tumefaciens-mediated transforming to trap genes in rice. Eighteen independent transgenic lines were obtained and propagated. T(2) generations of 18 independent transgenic lines were screening by herbicide (Basta) (Fig.2) and the herbicide-resistant plants obtained were analyzed by PCR (Fig.3). Ds element transposed in an inheritable manner was found in 37 plants, in which 5 plants showed GUS activity (Fig.4).