HKU Bulletin May 2020 (Vol.21 No.2)

Given that OsACBP2 contributes to boosting oil content as well as size and weight in transgenic rice grains, an application of this technology in rice is expected to benefit agriculture by increasing grain yield and composition to satisfy the need for more food. PROFESSOR MEE-LEN CHYE Professor Mee-Len Chye, Wilson and Amelia Wong Professor in Plant Biotechnology from the School of Biological Sciences, who led the research team, said: “Increasing grain size and yield, besides rice bran and seed lipid content, in crops such as rice is an important research area because one can grow a better (higher yielding) crop on the same area of land. That in turn means we do not need to clear more land for farming as the all-important forests will be in lower competition with farmland.” The breakthrough came when the team identified that when the protein, ACYL-COA- BINDING PROTEIN2 (OsACBP2) from rice (Oryza sativa) , is overexpressed in transgenic rice, it will enhance grain size and weight by 10 per cent and increase grain yield. “Before this discovery, ACBPs [acyl-CoA- binding proteins] were not known to affect grain size and weight,” said Professor Chye. “Further, as OsACBP2 is a lipid-binding protein that binds lipids such as acyl-CoA esters, the major precursors in seed oil production, it was not surprising that oil was observed to accumulate in the transgenic rice grains. Thus OsACBP2 could also enhance nutritional value with a 10 per cent increase in lipid content of rice bran and whole seeds. “Given that OsACBP2 contributes to boosting oil content as well as size and weight in transgenic rice grains, an application of this technology in rice is expected to benefit agriculture by increasing grain yield and composition to satisfy the need for more food.” Bioactive components And it is the right kind of food: rice bran oil has been shown to contain bioactive components that have been reported to help lower cholesterol, and it possesses anti- oxidation, anti-carcinogenic and anti-allergic inflammation activities. “This technology, if applied to other food crops, would not only help address food security but also elevate nutritional properties in grains,” she said. The findings have been published in The Plant Journal and an international patent has been filed. Asked how soon the technology could be put to widespread use, Professor Chye replied: “The bottleneck is at the planting and use of genetically- engineered crops/food. While these crops/ food are widely consumed in North America their status in Hong Kong appears less optimistic. Local granting bodies should support animal testing on these crops, as such experiments must be carried out next following our initial discoveries.” The findings are the result of many years’ research. Professor Chye started working on plant ACBPs when she set up her laboratory at HKU around 25 years ago. Prior to that she was in Professor Nam-Hai Chua’s Laboratory at the Institute of Molecular and Cell Biology, Singapore. “While there, I had prepared a cDNA library from Arabidopsis embryos for the laboratory and Professor Chua very generously allowed me to bring a few of the potentially interesting cDNA clones that I had identified to work on when I left to set up my own laboratory at HKU,” she said. “Of the six clones I brought, one encoded an ACBP, and thus the story began. The discovery by HKU plant biotechnology scientists of a protein that can not only increase rice yield but also enhance the grain’s composition and nutritional content marks an important step forward in food security on our crowded planet. CAPITAL GRAINS Nothing much was known on plant ACBPs then so I was very fortunate to stumble upon this niche. “In fact, only one form – that is, the smallest ACBP member – was well characterised in mammals and yeast then. We discovered there was an ACBP protein family of six members from the model plant, Arabidopsis, and later from rice, a crop we selected to work on. We first published on rice ACBPs in 2011.” Her partners on the research are postdoctoral fellows Dr Guo Zehua and Dr Shiu-Cheung Lung, as well as her long-term colleagues and collaborators Professor Edward Yeung from the University of Calgary, with whom she has been publishing since 2001, and Dr Richard Haslam, from Rothamsted Research (a well- established agricultural research institution in the United Kingdom) who provided expertise in lipid profiling, particularly using minute amounts of material. The research was funded by both the Research Grants Council of Hong Kong and the Wilson and Amelia Wong Endowment Fund, which supports Professor Chye’s Endowed Professorship in the School of Biological Sciences. Professor Chye concluded: “Increasing grain size and yield in crops such as rice is an important research area that aligns with the aspirations of Dr Wilson and Mrs Amelia Wong on the use of plant biotechnology for a sustainable future.” OsACBP2-overexpressing rice grains possess higher oil content. The research group led by Professor Chye identified a protein, ACYL-COA-BINDING PROTEIN2 (OsACBP2) from rice (Oryza sativa), that when overexpressed in transgenic rice, will enhance grain size and weight by 10 per cent and elevate grain yield. Grain oil content (µmol mg -1 ) OE-1 25 20 15 10 5 0 OE-3 OE-17 OE-21 VC ZH11 Controls OsACBP2- overexpressing lines VC ZH11 OE-1 OE-3 OE-17 OE-21 22 The University of Hong Kong Bulletin | May 2020 23 RESEARCH

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