Rice Allelopathy on Weed Control and Underlying Molecular Mechanism.

Rice Allelopathy on Weed Control and Underlying Molecular Mechanism

Changxun Fang^1,2, Wenxiong Lin^1,2*

1.        Fujian Provincial Key Laboratory of Agroecological Processing and Safety Monitoring (School of Life Sciences, Fujian Agriculture and Forestry University), Fuzhou 35002, People's Republic of China

2.     Key Laboratory of Crop Ecology and Molecular Physiology(Fujian Agriculture and Forestry University), Fujian Province University, Fuzhou 35002, People's Republic of China

Abstract: Rice allelopathy on weed had been reported for more than 20 years, and studies were well conducted in the last 10 years, however, the underlying mechanism has not been clearly elucidated. Regulation of gene expression is an initial response in plant interaction, and the miRNAs expression pattern on allelopathic rice PI312777 and its accompanied barndyardgrass (BYG) was investigated respectively by using high throughput sequencing technology. The results show that miRNAs relevant to plant hormone signal transduction, nucleotide excision repair, tropane, piperidine and pyridine alkaloid biosynthesis were enrich expressed on BYG, while only tropane, piperidine and pyridine alkaloid biosynthesis relative miRNAs were found enrichment on PI312777. Most of the enrich miRNAs from BYG that accompanied with PI312777 was enhanced up-regulated folds under elongation on co-cultured days, and it was peak at the 7^th day. The reverse was true in the condition of BYG co-cultured with non-allelopathic rice Lemont, based on the qPCR detection of miRNAs dynamic expression under different co-cultured days. Increasing of BYG numbers accompanied with PI312777 also resulted in enhanced gene expression folds of enrich miRNAs on these BYG. Overexpression of PAL gene on PI312777 contributes to increase the miRNAs expression on the accompanied BYG, and silence of PAL gene on PI312777 leads to a reverse result. The target genes were presented a revere expression pattern in contrast to their relevant miRNAs. Moreover, increasing of BYG numbers with PI312777 resulted in decreased the IAA content but increased the apurinic/apyrimidinic sites (AP sites) in the root of BYG, and the BYG accompanied with PAL-OE transgenic lines had lowest IAA content and largest AP sites, but the reverse was true in the BYG accompanied with PAL-RNAi transgenic lines, however, no significant difference was found in the BYG co-cultured with non-allelopathic rice Lemont. In addition, BYG under phenolic acid allelochemicals treatment showed greatly enhancement on the gene expression level of the enrich miRNAs, which in turn to reduce the target gene expression. However, no significant change was found on the BYG treated by terpenoids. Further determination on microbe population numbers in the hydroponic solution showed that a special microbe named Myxococcus species were closely correlated with rice allelopathy potential. The number of Myxococcus was significantly increased following the enhancing BYG density accompanied with PI312777, and hydroponic system of PAL-OE co-cultured with BYG contained highest Myxococcus numbers while the mono-cultured of PAL-RNAi lines had lowest Myxococcus contains, however, hydroponic solution from Lemont had lower Myxococcus numbers than PI312777 that under same treatment, and no significant difference was found among different ratios of Lemont/BYG co-cultured system. Phenolic acids contributed to increased Myxococcus numbers in the hydroponic solution, and the number was higher than that of terpenoids used. BYG co-cultured in sterile hydroponic solution contained Myxococcus showed increased gene expression level on the enrich miRNAs, and the miRNAs expression level was further enhanced in the condition of Myxococcus with its metabolisms, which indicated the important role of Myxococcus on rice allelopathy. According to the research, it was clear that rice allelopathy specially suppress the IAA synthesis and DNA damage repair on the surrounding BYG, by promoting of the enhanced expression on the relevant miRNAs, which in turn to inhibit BYG growth and development, and Myxococcus species play a vital part in the process of rice allelopathy on BYG.

Keywords:  Allelopathy, allelochemicals miRNA, Myxococcus, rice

E-mail:wenxiong181@163.com.

This work was supported by the National Research Foundation for the Doctoral Program of Higher Education of China (No. 20133515130001), National Natural Science Foundation of China (No. 31271670,U1205021), National Basic Research Program of China (973 Program, No. 2012CB126309) and 948 Project of Chinese Ministry of Agriculture (2014-Z36)