Effects of 6-Benzyladenine on Jatropha Gene Expression and Flower Development

Abstract

Jatropha curcas L. has been considered as a potential source of biodiesel feedstock due to its highly seed oil content. However, Jatropha exhibits low numbers of female flowers leading to insufficient seed yields for biodiesel production. Previous studies showed that application of 6-benzyladenine (BA) on Jatropha flower buds significantly increased female flower numbers and seed yield. However, the underlining molecular mechanism remained unclear. In this study, 160 mg/L of BA was applied on the Jatropha flower buds. As a result, BA significantly increased female flowers, male flowers, and seed yield (P < 0.05). BA also affected the inflorescences area, number and length of pedicel, all of which were appreciably greater than control (P < 0.05). The effect of BA to flower bud development was observed using Scanning Electron Microscope (SEM). SEM revealed that the stages of floral development between control and BA-treatment were similar indicating that BA might affect floral development at the transcriptomic level. Flower buds at 0, 4, and 24 h were selected based on the presence of sex organs for genes involved in flower development investigation. The expression analysis of 23 genes showed that CYTOKININ OXIDASE/DEHYDROGENASE5 (JcCKX5) was highly expressed at the transition stage (P< 0.05) subsequently enhanced the inflorescences area, increased organogenic capacity and ovule primordia formation. Moreover, application of BA increased the expression of SUPERMAN (JcSUP) and decreased the expression of TASSELSEED2 (JcTS2) during sex organs differentiated stage. Therefore, JcSUP might play a role in female flower formation parallel with arrested stamen formation through the down-regulation of JcTS2.