Abstract:

To understand the function of PuBBX24 in pear growth and development process，the gene of PuBBX24 and its promoter sequence were cloned from Pyrus ussuriensis seedling for molecular biological analysis. The spatial expression pattern of PuBBX24 was analyzed in roots，stems，leaves，flowers，and fruits. The cis-elements of PuBBX24 promoter were predicted and subsequently transferred into Arabidopsis with GUS gene for spatial-temporal，as well as under conditions of ABA，different light and other abiotic stresses analysis of its activity. The function of PuBBX24 was also heterologously analyzed in Arabidopsis. The results showed that PuBBX24 had different expression patterns in roots，stems，leaves，flowers，and fruits，with the highest expression level in stems and lowest expression level in leaves. The PuBBX24 expression level decreased gradually in the leaves from juvenile to adult period. A series of cis-elements of PuBBX24 promoter were found with annotations of hormone-responsive，light-responsive and stress-responsive elements. The expression of GUS in transgenic Arabidopsis was mainly detected in leaves，hypocotyls，and sepals，with no uniform levels in roots，lower level in stigma and pedicel. In addition，GUS showed a gradually decreased expression pattern in the rosette leaves from juvenile to adult period and undetectable GUS activity was found in silique. PuBBX24 promoter showed obvious response to stresses of ABA，light，low temperature，osmosis and salt treatments，and over-expression of PuBBX24 in Arabidopsis affected the juvenile-adult transition. These results indicated that PuBBX24 might be involved in responses to ABA，light，and other abiotic stresses and play an important role in regulating the juvenile-adult transition process.

Key words: Pyrus ussuriensis, PuBBX24, expression pattern, promoter, juvenile period