The Hormonal And Molecular Mechanism Of The Transformation Between Germination And Dormancy Of Rice Tiller Buds

Tillering is an important agronomic trait of rice.In the present study,external nitrogen application,external hormones application and panicle removal were used to construct a series materials which were different from the tiller buds growth.The hormonal changes,genes and proteins expression changes related to rice tiller buds growth were emphatically measured to investigate the mechanism of hormonal and molecular regulation of the transformation between dormancy and germination of the tiller buds.The main results of the study are listed below.(1)Auxin,cytokinin(CK)and strigolactones(SLs)are three major hormones which regulate rice tiller buds outgrowth,but their interaction was unclear in rice.In the present study,we found that auxin in stems could inhibit and promote the second messenger,CK and SLs,respectively.CK and SLs could transport to buds,promoting and inhibiting buds outgrowth through regulating FC1 expression in buds.In addition,CK was proved to inhibit SLs synthesis,however SLs may have no effect on CK synthesis.SLs was shown to reduce IAA contents and auxin transport capacity in stems,while CK may not.Nitrogen application significantly inhibited SLs synthesis,which may caused by the promotion of CK synthesis.Furthermore,panicle removal significantly reduced IAA contents in stems,resulting in the inhibition and promotion of CK and SLs synthesis,respectively.(2)A comparative proteomic analysis was carried out to analyze the different levels of expression of proteins under nitrogen,NAA application,and decapitation.The results showed that nitrogen and NAA both regulated proteins related to energy,metabolism,stress responses,protein synthesis and protein degradation.In addition,NAA could also regulate proteins related to CK synthesis,ABA signaling,auxin signal transduction and transport.At the full-heading stage,several proteins in this study involved in signal transduction and cytokinin biosynthesis were identified by decapitation,which may play an important role in the mechanism of apical dominance.(3)iTRAQ and GeneChip provide quantitative measures of proteomic and transcriptomic in studing the mechanism of bud outgrowth under apical dominance in rice.Lots of genes and proteins were identified differentially expressed,participating in hormone synthesis and signal transduction.We found auxin,CK and brassinosteroid sinaling were required in promoting bud outgrowth,and ABA signaling negatively regulated bud germination.In addition,auxin synthesis and export in buds contribute to the germination and subsequent outgrowth of buds,in dormant buds,auxin failed to export through preventing PIN polarization,which was required in auxin transport.We also found the possible effect of CK in regulating cell cycle,which may act in triggering buds germination.