Identification of the genes responsible for these traits showed that they control gibberellin metabolism and/or perception. Dwarf mutants have been extensively analyzed for their inheritance and their response to plant hormones. There are various reasons for their dwarf phenotypes, associated with, for example, gibberellins, brassinosteroids, abnormal cell walls and abnormal cell elongation. Dwarf mutants deficient in endogenous GAs have been described for several plant species. Chinese chestnut is one of the important fruit native resources in China but its yield is limited because of lots of male flowers and a few female flowers. One aim in chestnut breeding is to select less male flowers and the high ratio of female to male inflorescences. Short catkins contribute to increase in production of chestnut production and breeding by reducing the nutrient consumption of trees. We have reported that the sck1 is a short catkins mutation which is a rare germplasm resource in chestnut. We investigated the hormone levels in the sck1 and it is shown that lower endogenous GAs levels but not other phytohormones. In maize, tomato, rice, sunflower and Arabidopsis, severe reductions in endogenous GA levels or GA response prevent normal anther, pollen development and pollen tube growth. It is very interested that except for short catkins, there are not any other significant different phenotypes between the sck1 and wild-type in leaf size, phenophase, morphology of bur, nut rate, weight and quality of nut, and the endogenous GAs levels are normal in vegetative part and lower in reproductive organ, but its mechanism is not clear. The endogenous levels of GAs and the response to exogenous hormone treatments suggested that the sck1 was likely impaired in GA biosynthesis. The exact size of the chestnut genome is unknown, but it’s thought to fall somewhere between the smallest plant genome and one of the larger genomes. LY294002 According the information from Fagaceae database, we analyzed that there is a small gene family of KAO candidates in chestnut and we isolated one from Chinese chestnut. It has high similarity to Lactuca sativa LsKAO1, AtKAO1 and AtKAO2 of Arabidopsis, CmKAO1 of pumpkin and the two KAO genes of pea. There is no difference in gene coding region of KAO between wild-type and the sck1. It is very interested that one point mutation was found in the promoter region of KAO, and the T convert to A at the upstream of translation initiation site in the sck1. The mutation may cause the decrease of the transcript of KAO in the sck1. But because of the requirement of a long incubation time from transformant screening to bearing fruit, it will spend us long time to confirm the function of the promoter of KAO. It is very difficult to establish a stable transgenic expression system in fruit trees. However, this is the key constraint to the development of molecular biology in fruit trees. The transgenic technology through embryogenesis on American chestnut and European chestnut had established. Embryogenesis of C. mollissima is few reported, because the most tissue culture of Chinese chestnut is organogenesis and the transgenic on Chinese chestnut had not been reported. We try to establish a kind of transgenic transient expression method in chestnut. The transient over-expressing KAO in the sck1 can partially rescue the short catkins by average 4–5 fold and could avoid the programmed cell death. Although we don’t know the mechanism, it may be caused by the increase the KAO expression in the early transient expression.