Abstract: Fingered citron（Citrus medica L. var. sarcodactylis Swingle），a variant of citron（C. medica L.），has a close genetic relation with citron while huge difference in fruit shape. The fingers of ‘Qingpi’，a fingered citron，commonly stretch out，but rolled up to form a fist when cultured under 20 ℃ during flower formation. Paraffin sections revealed that the inner carpel of the fist-like citron partially fused before anthesis. qRT-PCR technology was used to analyze the expression patterns of CRC in fingered citron，fist-like fingered citron，and the citron during the entire stages of flower development. The result shows that the expression pattern of CRC in fingered citron was significantly lower the other two. In addition，the expression pattern of fist-like fingered citron was quite close to that of the citron. It implied that the fruit shape difference is associated with the CRC gene expression patterns. The full length of CRC gene was identified from fingered citron and citron. Compared with citron，the promoter of CRC in fingered citron lacked two TATA-Box elements. Both CRC promoters in fingered citron and citron were transiently transformed into N. benthamiana leaves. It shows that the activity of CRC promoter from the fingered citron was lower than that from the citron under room temperature. When cultured under low temperature（4 ℃），CRC promoters activities were enhanced either for the fingered citron or the citron. However，the promoter activity in the fingered citron was much more stronger than that in the citron. It indicates that the promoter of fingered citron is more sensitive to low temperature than that of citron. Therefore，CmsCRC maybe involved in regulating the fingers stretch in fingered citron and activated by lower temperature.

Key words: fingered citron, CmsCRC, fruit shape, promoter activity, low temperature, carpel fusion