CHARACTERISATION OF HORDEUM VULGARE CELLULOSE SYNTHASE-LIKE F6 PROMOTER VIA TRANSGENE EXPRESSION IN RICE

Beta-glucan in cereal crops is known as a functional food, which can reduce cardiovascular diseases by lowering blood cholesterol levels. However, beta-glucan content is relatively low in rice grains, despite being relatively abundant in barley and oat grains. Taking advantage of rice as the staple food for Asians, increasing beta-glucan content in rice for their consumption may help to reduce cardiovascular-related diseases among them. Previous attempts in increasing beta-glucan content in rice via transgene expression of beta-glucan synthase genes from barley into rice were unsuccessful due to the use of non-tissue specific as well as constitutively expressing promoter. The current transgenic expression study was performed to characterise the promoter of beta-glucan synthase gene in barley using beta-glucuronidase (GUS) reporter gene. Two fragments of HvCslF6 promoter (2771 bp and 1257 bp) were successfully fused with GUS reporter gene and integrated into rice plants, demonstrated that the promoter was functional in the heterologous plant system. The presence of blue GUS staining was observed on the leaf, root, stem, and grain of the transgenic rice regardless of the promoter length used and stayed functional up to the next generation. GUS qualitative analysis confirmed that the shorter promoter length generated a stronger GUS activity in comparison to the longer one. This indicated that the presence of repressor elements in between the -2771 bp and -1257 bp regions. The preliminary results shed light on the strong promoter activity in the rice endosperm tissue. It can become an alternative to the collection of plant promoters that can be used for grain quality improvement and biofortification.

Promoter PPSP1–5-BnPSP-1 From Ramie (Boehmeria nivea L. Gaud.) Can Drive Phloem-Specific GUS Expression in Arabidopsis thaliana

Isolation of phloem-specific promoters is one of the basic conditions for improving the fiber development and resistance of ramie phloem using genetic engineering. In this study, we isolated a ramie endogenous promoter (named PPSP1-BnPSP-1) and analyzed the function of its truncated fragments in Arabidopsis. The results show that PPSP1-BnPSP-1 can drive the GUS reporter gene to be specifically expressed in the veins of Arabidopsis. After hormone and simulated drought treatment of the independent Arabidopsis lines carrying PPSP1-BnPSP-1 and its truncated fragments, only PPSP1–5-BnPSP-1 (−600 to −1 bp region of PPSP1-BnPSP-1) is stably expressed and exhibits phloem specificity. Our findings suggest that PPSP1–5-BnPSP-1 can be used as a phloem specific promoter for further research.

Ectopic Expression of a Fagopyrum esculentum APETALA1 Ortholog only Rescues Sepal Development in Arabidopsis ap1 Mutant

Fagopyrum esculentum (Polygonaceae: Caryophyllales) exhibits an undifferentiated perianth comprising five showy tepals, which does not completely correspond to the perianth differentiated into typical sepals and petals in most core eudicots. In Arabidopsis, the APETALA1 (AP1) gene is involved in specifying sepals and petals development. Here we isolated AP1 ortholog, FaesAP1, and a 2.2kb FaesAP1 promoter (pFaesAP1) from F. esculentum. FaesAP1 expression is mainly detectable in all floral organs and maintains at a high level when tepals elongate rapidly both in pin and thrum flowers. Moreover, the GUS reporter gene driven by pFaesAP1 was activated in flowers where the sepals were intense, but the petals very weak or absent. Additionally, FaesAP1 ectopic expression in Arabidopsis ap1-10 mutant rescues sepal development fully, obviously prompting early flowering, but failing to complement petal development. In this study, evidence was provided that the showy tepals in the F. esculentum are homologs to core eudicots sepals. Furthermore, these findings show a different perianth identity program in Caryophyllales, suggesting that AP1 orthologs involved in petal development may evolve independently across different clades of core eudicots. Our results also suggest that FaesAP1 holds potential for biotechnical engineering to develop early flowering varieties of F. esculentum.