OsKSL4 RNAi In Allelopathic Rice And Its Effect On The Suppression On The Target Weed Plant

Rice,as one of the most important food crops in the world,of which 3%-4%varieties show allelopathic potential to inhibit the growing of accompanying weed in the field.Allelochemicals have a significant allelopathic effect on weed suppression.Recently,studies found that momilactone B releases from rice plays an important role in inhibiting growing of some other plants in lad condition,but it still remains not to be clearly understood in the field condition.In this study,OsKSL4(Kaurene synthase 4)gene,the key gene for momilactone B synthesis,was taken as target gene and its functional fragment was cloned from allelopathic rice PI312777,with the aim to construct a OsKSL4 interference vector for genetic transformation of rice.The positive transgenic rice was then used to evaluate the changes of allelopathic potential in comparison to wild type plants(WT)by pot experiment under field conditions.In order to learn the relationship between momilactones and rhizospheric process of rice allelopathy,the study further comparison of the bacterial diversity and quantity as well as fungal quantity between the two different rice rhizospheric soil.The results are showed as follows:According to the result of semi-quantitative PCR detection,down-regulating of OsKSL4 gene in OsKSL4-RNAi transgenic rice was found,then we put different cultivars of rice co-culturing with BYG(12:12)and mono-plant BYG(24)was used as control.The change of BYG dry weight was compared after 4 weeks,it was found that the dry weight of BYG co-cultured with OsKSL4-RNAi was more than that of co-cultured with PI-pTCK303 or PI,but no significant different was found.Simultaneously,dry weight of BYG co-cultured with rice was significant less than control BYG,the results indicated that transgenic rice and its wild type plants have equivalent weed suppression capability.With T-RFLP technique,we then analyzed different rice rhizosphere soil bacterial communities,the results showed bacterial community structure of rhizosphere soil from each rice/BYG co-cultured system was similar;while compared to those without BYQ it was found the bacterial diversity was increased by accompanying BYG Griseus,which is able to degrade diterpenoid,was detected in the wild-type PI312777 rhizosphere soil,but not in transgenic plants rhizosphere soil.At the same time,qRT-PCR was employed to detecting population number changes of bacteria and fungi from different allelopathic rice rhizosphere soil,the result demonstrated that transgenic rice OsKSL4-RNAi and wild type PI co-cultured with BYG have significantly higher population number of bacteria and fungi than those without BYGIn conclusion,after inhibiting the expression of momilactones synthesis relative gene(OsKSL4),there is no obvious change on allelopathic potential for transgenic plants in actual soil cultivation environment,it may be caused by the soil microbe.By microbial transformation,momilactones was possibly degraded,and its allelopathic weed-suppression capability decreased.This finds provides a theoretical basis for deeply evaluating allelopathic potential of momilactones in actual cultivation environment.