Starch is one of the major components of many fruits, such as apple and banana, and has a high influence on fruit quality.  For instance, apples with low starch content taste sweet, and some varieties, such as Granny Smith, that contain high starch content are deemed good cooking apples. However, little is known about the molecular mechanism underlying starch synthesis in fruits.  A recent research result released by Prof. HAN Yuepeng and his research group may provides insights into this question.

Starch is a carbohydrate which consists of two types of molecules: amylopectin and amylose. The synthesis of amylose is catalyzed by granule-bound starch synthase (GBSS). Prof. Han’s lab isolated and characterized all members of genes encoding GBSS in three fruit trees, including apple, peach, and orange. Their results showed that the expression level of GBSS genes is higher in apple than in peach and orange. Starch accumulates in apple fruit throughout development, and represents a major component. In contrast, sugars are the main carbohydrates in both peach and orange fruits. Therefore, their results suggest that high levels of expression of GBSS genes contribute to starch accumulation in apple fruit. Phylogenetic analysis showed that GBSS gene in an ancestral angiosperm must have undergone genome duplication ~ 251 million years ago to generate two families, GBSSI and GBSSII. Both GBSSI and GBSSII are found in monocots; however, GBSSI is absent in eudicots. In monocots, GBSSI genes are exclusively expressed in endosperms, which are usually absent in mature seeds of eudicots. This fact might be responsible for the loss of GBSSI genes in eudicots.

The study entitled “Diversification of Genes Encoding Granule-Bound StarchSynthase in Monocots and Dicots Is Marked by Multiple Genome-Wide Duplication Events” has been published in PLoS One.

Article link: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030088 

Author contact: Prof. HAN Yuepeng

Tel: +86-27-87510872

Email: yphan@wbgcas.cn