Analyze On Differential Expression Of Drought-resistance Related MicroRNAs In Cassava

Cassava (Manihot esculenta crantz)is the Manihot in Euphorbiaceae. It is a important food crops, its high productivity and its ability to withstand a variety of environmental conditions (including significant water stress) in typical tropical area. It is also an important industrial raw material for our starch and fuel ethanol production. microRNA (miRNA) is a class of-21nt non-coding RNAs that regulate mRNAs at the post-transcriptional level. miRNAs are key regulators of nearly all essential biological processes. This study is a further research on characteristic of drought-related miRNA in our preliminary cassava miRNA study.To elucidate their functions in drought responses,5 experimental-proven stress-related miRNAs in computernal miRNA precidtion and 11 new stress-related miRNAs in miRNA deep solexa sequencing were choosed, and further verified and profiled the expression of 16 miRNAs in two different drought-resistance varieties under three kinds of drought stress treatments. The results revealed that those miRNA have some characteristic of species and condition-specific dependence, their expression pattern were much more uncertainty and diversity Compared with theose of early expereiment, Specific performance is as follows:(1) As the results of qRT-PCR shows, only one new sequenced miRNA not expressed in all given drought treatment,15 of the 16 miRNAs were experimentally verified in at least one of drought-treated materials, and the expression level were diverse largely among different time point, different tissues as well as different treatment. Overall, miRNA expression is mainly up-regulated expression (overexpression account for 41%,9% down-regulated expression, no expression 50%) compared with the control.(2) In our three kinds of drought-stress treatments (DA, DH, DNH),6 miRNAs (1045125,1229496,1230481,3615546,3747522 and 5178028) expressed in DA and DH, but silenced in DNH; miRNA171ab only expressed in DH except for DA and DNH; 4 miRNAs (390b,399e,4806982 and 6915202) expressed in DH and DNH。miRNAs that showed differential expression in different conditions, implied that their targeted genes involved in different regulated pathway under drought stress。(3) Expression pattern analysis showed that 15 miRNA has a large different expression manner in three kinds of drought. Reflecting apparent Sequential-specific characters; At each treatment, the number of miRNA similar expression patterns are small, showing obvious tissue-specific. comparing different tissue of same treatment and same variety, SC124 and KU50 in DA treatment, only three (6915202,3747522,3615546) and 5 (1229496,1230481, 3615546,4806982,5815094) were expressed similarly in leaves and roots, respectively, In DH Treatment, number of similar expression pattern changed to 5 (1229496,4806982, 5178028,5815094,3615546) and 0, In DNH treantment, were three (3615546,4806982, 5815094) and 1 (398b); In addition, the six comparision of different variety in same treatment and same tissue, variety-specific performance is more obvious in the three treatments, there were no one miRNA expression patterns are similar between SC124 and KU50.(4) The all 5 stress-related miRNAs (166a,171ab,390b,398b and 399e) were expressed in this drought treatment, reveals that the 5 miRNAs are all stress-induced and drought-responses correlated. Comparision with pool mixture of tissue and time point in preliminary studies, The experimental treatment manner, tissue and time point is more detailed and the samples are all separated tissuely and timely, the results more clearer and deeper:In view of stress treatment,5 miRNAs are not expressed in the DA, but expressed in the DH and DNH treatment; In point of tissues characters,166a and 171ab are expressed only in roots, not expressed in the functional leaves, Three miRNA (399e,398b and 390b) expressed in both leaves and roots; In aspect of timing on the stress response,166a expressed in time point 1 of roots in the DNH treatment, but not in time points 2 and 3, other 4 miRNAs shows significant expression in the 3 time points of root or functional leaves of two variety in three drought treatments.(5) Finally, we predicted 162 miRNA:target binding partners between 16 miRNA and their targeted mRNAs by the Software of Hitsensor, and it remain to identify the targets cleavage sites of miRNAs that interented us in future experiments.In this study, we make a further collection of cassava and drought-related miRNA and its target gene, these findings has laid a further foundation for future research on mechanisms of drought-resistant miRNA and genetic improvement of drought adaptation in cassava.