[Research progress of relationship between continuous cropping obstacles and microRNAs in Rehmannia glutinosa].

The efficacy of Rehmannia glutinosa which as a large quantity of traditional Chinese medicine is significant. However, the land must be given up after one season of R. glutinosa cultivation or replanted after a period of 8-10 years because of the severe continuous cropping obstacles. MicroRNAs is a class of endogenous non-coding small RNAs, which participate in regulation of physiological activities by target mRNA cleavage or translational repression in plants. In recent years,studies on the role of miRNAs in plants have made significant progresses,especially in medicinal plants．MiRNAs from some different medicinal plant species have been identified with regulatory effects．When plants are exposed to environmental stress, miRNAs act on stress-related genes and initiate stress-resistance mechanisms in the body against adverse factors. R. glutinosa is also a kind of environmental stress. It is conducive to deciphering the molecular mechanism of continuous cropping obstacles for us by researching miRNAs. This article reviews the production of miRNAs, mechanism, research approaches and characteristics of resisting the environmental stresses in plants, the development trends and future prospect of R. glutinosa miRNAs research.

[Advances on molecular mechanisms of Rehmannia glutinosa consecutive monoculture problem formation in multi-omics era].

Although consecutive monoculture problems have been studied for many years, no effective treatments are currently available. The complexity of systems triggered the formation of consecutive monoculture problems was one major cause. This paper elaborated the physiological and ecological mechanisms of consecutive monoculture problem formation based on the interaction relationship among multiple factors presented in the rhizosphere soil of consecutive monoculture plants. At same time, in this paper the multiple interactions among cultivated medicinal plants, autotoxic allelochemicals and rhizosphere microbial were proposed to be most important causes that derived the formation of consecutive monoculture problem. The paper also highlighted the advantage of 'omics' technologies integrating plant functional genomics and metabolomics as well as microbial macro-omics in understanding the multiple factor interaction under a particular ecological environment. Additionally, taking R. glutinosa as an example, the paper reviewed the molecular mechanism for the formation of R. glutinosa consecutive monoculture problem from the perspective of the accumulation of allelopathic autotoxins, the rhizosphere microecology catastrophe and theresponding of consecutive monoculture plants. Simultaneously, the roles of mutilple 'omics' technologies in comprehending these formation mechanism were described in detail. This paper provides finally a new insight to solve systematically the mechanism of consecutive monoculture problem formation on molecular level.

[Correlation of Allelopathy of Rehmannia glutinosa Root Exudates and Their Phenolic Acids Contents].

OBJECTIVE: To study the allelopathic potential of Rehmannia glutinosa root exudates in different growth stages and dynamic change of phenolic acids contents, in order to reveal the correlation between phenolic acids and allelbpathy effect of Rehmannia glutinosa. METHODS: Root exudates of Rehmannia glutinosa in different growth stages were obtained by a new instrument which was used to collect the root exudates of xerophytes. After that, bioassay was applied to estimate allelopathy effect of the root exudates. HPLC was used to determine the contents of five phenolic acids (coumaric acid, 4-hydroxybenzoic acid, vanillic acid, syringic acid and ferulic acid) which were reported to relate to allelopathy effect. Correlation of bioassay data and HPLC data were also analyzed. RESULTS: The germination rate of radish after soaking by root exudates of different growth stages of Rehmannia glutinosa was 97. 89%, 92. 38%, 89. 52%, 85. 71%, 85. 71%, 84. 76% and 83. 81%, respectively, which indicated a decline trend. And significant differences were shown from previous enlargement stage compared with the contrast. The bud length after soaking by root exudates was 5. 68, 5. 76, 5. 91, 5. 65, 5. 41, 5. 28 and 5. 11 cm, separately, which increased slightly before decreasing gradually. Previous enlargement stage was also the initial period when significant differences were shown. Five phenolic acids were detected in root exudates by HPLC, while the change of their contents and the allelopathy effect of root exudates did not perform a similar trend. Correlation analysis indicated the five phenolic acids did not have significant relevance (r = - 0. 666 - 0. 590) with germination rate and bud length of radish except the negative correlation (r = -0. 833, P <0. 05) of syringic acid and bud length. CONCLUSION: Significant allelopathy effect of Rehmannia glutinosa is performed from previous enlargement stage and enhanced with its growth. Syringic acid is a probable dominant allelochemical of Rehmannia glutinosa.

[Cloning and expression analysis of the expansin gene RgEXPA10 in Rehmannia glutinosa].

Using cDNA from Rehmannia glutinosa leaf as template, a 972 bp fragment of expansin gene which containing a 762 bp ORF that encoded 253 amino acids, was cloned, named RgEXPA10, which GenBank accession number for this gene is KF011918. A 1 207 bp genomic sequence of RgEXPA10 was amplified by PCR with leaf DNA as template, sequencing analysis revealed that three exons and two introns in RgEXPA10 genomic sequence, and which GenBank accession number is KF011919. Molecular and bioinformatic analyses indicated that RgEXPA10 protein have DPBB_1 and Pollen_allerg_1 domain, also including a 26 aa nuclear localization signal and a 19 aa transmembrane region. Phylogenetic analysis revealed that RgEXPA10 showed the highest homology with AtEXPA8 among the 26 α-expansins in Arabidopsis thaliana. However, the RgEXPA10 indicated the highest homology with the expansin from Solanum lycopersicum among 22 plant species. Expression patterns using qRT-PCR analysis showed that RgEXPA10 mainly expressed in unfolded leaf, followed by the tuberous root at stage of expanding period, and rarely expressed in senescing leaf. And RgEXPA10 showed higher expression level in tuberous root at 60 and 90 days after emergence. The transcription level of RgEXPA10 significantly reduced under all the three stresses including continuous cropping conditions, salinity and waterlogging. This study will lay foundations for molecular function in development and regulation of different stresses for R. glutinosa.