Response Of Flowering Related Genes To Environmental Changes In Roses

As everyone knows,the flowering transition of plants is affected by the internal factors（hormone,age,autonomy）and external environmental factors（temperature,photoperiod）,and can only be triggered when various environmental conditions are suitable.Roses mainly have two flowering modes:continuous-flowering and once-flowering.Among them,the once-flowering roses can only blossom in early spring,while the continuous-flowering roses can keep on transforming into flowers under the constantly changing external environment.But its regulation mechanism is,as yet,unclear.In this study,it is continuous-flowering Rosa chinensis‘Old Blush’and once-flowering Rosa‘Huan Die’that were used as experimental materials.With flowering of Rosa‘Huan Die’into comparison,I observed the flower bud differentiation process of‘Old Blush’and‘Huan Die’by paraffin method.Refer to the flowering regulation network,18 candidate genes related flowering were selected from the comparative transcriptome of continuous/once-flowering rose.Then,the expression pattern of candidate genes and endogenous hormones were determinated by q RT-PCR and ELISA during flowering transition in three different environments,respectively.Accordingly,in order to provide basis for elucidate the molecular mechanism;In this study,we explored how continuous-flowering rose induces flowering under different environments.The main conclusions are as follows:（1）The microscopic observation of paraffin section found that the morphology mark of‘Old Blush’and‘Huan Die’starting from vegetative growth to reproductive growth is consistent,which is the growth cone widens and flattens from a raised one.In addition,‘Old Blush’and‘Huan Die’begin to flower when the buds are stretched to 4-5mm（5 days after pollard）and 7-8 mature compound leaves are unfolded,respectively.The flower bud differentiation of‘Old Blush’is significantly faster than‘Huan Die’.‘Old Blush’only takes 1-2 weeks to complete the flower transformation,while‘Huan Die’takes about 3 months（from March to May 2019）.（2）Eighteen candidate genes（VIL 1,VIL 2a,VIL 2b,FRI 5,FRI 3,FRI 1,CO,CO like 2,SPL3,AP2 like,SVP,FT,FT like,FD,FLC,FCA,SOC 1,LFY）were differentially expressed in continuous and once-flowering roses.The results of expression pattern analysis show that under three different environmental conditions,the downstream integration factors,such as FD,FT,SOC1 and LFY,participated in flowering regulation of‘Old Blush’each time.However,it is not regulated by upstream genes in each pathway,and there may be other factors or pathways to regulate the integration factors in the downstream of the flowering network,and such factors or pathways are not influenced by environmental changes.（3）Through the bio-informatics analysis of FD,FT,SOC1,LFY,the results showed that the four genes may have multiple post-translational regulatory roles,and its expression level may be regulated by various factors such as hormones（abscisic acid,gibberellin,auxin）,temperature,drought and light.In addition,thirty-one possible upstream binding factors were selected from transcriptome data.（4）The results of hormone determination showed that the expression levels of IAA,CTK,GA₃and ABA were consistent in‘Old Blush’and‘Huan Die’.Among them,IAA,CTK and ABA promoted flower formation in different environments of‘Old Blush’and‘Huan Die’,while GA₃only promoted flower formation in‘Huan Die’and inhibited flower formation in‘Old Blush’.These hormones may also affect the expression of FT,FD,SOC1 and LFY.Among them,IAA and ABA may promote the expression of FT,FD,SOC1 and LFY in‘Old Blush’and LFY in‘Huan Die’.GA₃may promote the expression of LFY in‘Huan Die’,but not in‘Old Blush’.In summary,the results showed that four genes（FT,FD,SOC1 and LFY）were involved in the flower forming process of‘Old Blush’under different environments.In addition,thirty-one possible upstream binding factors were predicted,and hormones might also affect their expression levels.The results provide new information to elucidate the continuous-flowering mechanism of rose.