Bulletin Spring‧Summer 1996

A genetic linkage map of Xianggu Mushroom Key: • I - X I I I : N u m b e r s given to 13 l i n k a g e r o u ps (each r o u g h l y c o r r e s p o n d i n gto a chromosome) • A l p h b e t s andf i g u r e s on the r i g h t : Names of m a r k e r s , 62 in all ( a l p h a b e t s r e p r e s e n t i n g p r i m e r s and f i g u r e s i n d i c a t i n gthe number of bases) • F i g u r e s on the left: R e l a t i v e genetic distance s ( in c M) between m a r k e r s , a d d i ng up to give total genetic d i s t a n c e of each g r o up Fruiting Body Development Fruiting body development refers to the actual process of fungal growing from mycelium into mushrooms. It is a very complex process which has been poorly studied in the past. Advances in the polymerase-chain-reaction-based RNA fingerprinting method have now enabled researchers to identify and clone genes that are expressed specifically during Xianggu's fruiting body development. More than 10 putative 'fruiting genes' have been identified, several have been cloned and analysed, and more are expected to undergo these processes. The functions of these genes can be inferred by comparing their DNA sequence wit h the known genes in the GeneBank of the National Center for Biotechnological Information in the United States. The information thus acquired will be used to identify the key steps during fruiting body development and to construct a model of the process. ‘Fruiting genes' may also be manipulated to shorten th e fruiting process and to increase yields. Degradation of Lignocellulosic Materials Mushrooms do not carry out photosynthesis but rely on extracellular enzymes to degrade complex organic matters into soluble substances as nutrition. As materials that are most widely adopted as growth substrates for mushrooms are lignocellulosic, researchers in Prof. Kwan's laboratory want also to identify gene s that are expressed specifically during g r ow t h on lignocellulosic substrates. They do it by RNA fingerprinting and other approaches, and a relevan t gene has been identified and cloned. This gene can be shuttled back into the mushroom to improve growth and fruiting efficiency. Wide Applicability of Research Results Many researchers are now beginning to delve into the myriads of possibilities of the Xianggu mushroom, such as using it to make health foods and for seasoning, analysing its anti-tumour/antiviral properties, and tapping its other medicinal potentials. Growing better mushrooms tomorrow will certainly affect more than just the palate. • Prof. Kwan Hoi-shan received his Ph.D. from the University of California at Davis in 1982 and is currently associate professor in the Department of Biology at The Chinese University of Hong Kong. His research interests include molecular genetic analysis of edible mushrooms (Lentinula edodes) for strain typing, genetic maps, and breeding programmes; molecular cloning, analysis and utilization of cellulose and ligninase genesfrom edible mushrooms; and molecular genetic studies of fruit-body development of shiitake mushrooms (Lentinula edodes). Since 1986, Prof. Kwan has been the recipient of five RGC/UGC Earmarked Research Grants and three Croucher Foundation Research Grants. 27