Changes in microRNAs expression of flax (Linum usitatissimum L.) planted in a cadmium-contaminated soil following the inoculation with root symbiotic fungi.

Cadmium is one of the most harmful heavy metals that harm agricultural products. Evaluating microRNAs expression is a new and accurate method to study plant response in various environmental conditions. So this study aimed to evaluate the contribution of two symbiotic fungi in improving flax tolerance in a Cd-polluted soil using microRNAs and their target gene expression. A factorial pot experiment in a completely randomized design was conducted with different levels of Cd (0, 20, and 40 mg kg-1) on non-inoculated and inoculated flax with Claroideoglomus etunicatum and Serendipita indica. The results presented that increasing Cd levels caused a constant decline of alkaline phosphatase of soil (from 243 to 210 and 153 µg PNP g-1 h-1), respectively, from control (Cd0) to 20 and 40 mg Cd kg-1. However, the inoculation of flax with fungi significantly enhanced these properties. A negative correlation was observed between the expression level of microRNA 167 and microRNA 398 with their corresponding target genes, auxin response factor 8 and superoxide dismutase zinc/copper 1, respectively. The expression level of both microRNAs and their targets indicated that the inoculation with symbiont fungi could diminish Cd stress and enhance the growth of flax.

Soil contamination with Cd affects plant growth.Root symbiotic fungi can improve plant growth in Cd-polluted soils.Examining microRNA expression is a new and accurate method to evaluate plant response to Cd pollution and symbiotic fungi.

Comparative analysis of differentially expressed miRNAs in leaves of three sugarcanes (Saacharum officinarum L.) cultivars during salinity stress.

BACKGROUND: Sugarcane is an important industrial plant cultivated mostlyin the arid and semiarid regions. Due to climate change and anthropogenic activities, the sugarcane fieldsare prone to be damagedas a result of salt deposition. The consequence of such phenomena is turning to become a major thread in sugarcane cultivation. To address this issue, the identification of salinity tolerant cultivars would be a suitable strategy to minimize yield loss in the area. It is well known thatthe expression of abiotic stress-responsive genes including noncoding microRNAs (miRNAs) and their codingtargetscould lead to enhancement of stress tolerance in crops. Therefore, the expression study of those noncoding and coding genes under stress conditions is an appropriate approach to screen the tolerant cultivars. In addition, the examination of the expression of miRNA's target genes could provide deeper insight into the molecular stress mechanism and facilitate the identification of tolerant cultivars. METHODS AND RESULTS: We aimedto assess the expression of nine candidate miRNAsand their corresponding targeted genes among the studied sugarcane cultivars under high salinity conditions, leading to the identification of the salt-tolerant cultivar. To achieve our goal, a two-factorial experiment with three sugarcane cultivars (CP-48, CP-57, CP-69) and two salinity levels (0 and 8 ds/m) was conducted. The result indicated significant differences in expression with in miRNAs and also their target genes. The highest reduction of miRNAs expression occurred in miR160 while the lowest oneappeared in miR1432. The data also indicated that the higher and the lowest expression of targeted genes occurred in miR160 and miR393 respectively. Among studied cultivars, the CP-57 showed poor performance while CP-69 expresses a superior tolerance to salt stress. CONCLUSIONS: Taken together, these results suggested that the monitoring of microRNA expressioncould provide a new approach forthe screening of well-adapted cultivars under salt conditions. Such an approach would be the appropriate solutionto combat plant stress inhigh salinity region/soil. Our result indicated that the miR160 generates sugarcane tolerant to salt stress, can be potentially be used as a biomarker to salt stress.

Biochemical and molecular investigation of non-rhizobial endophytic bacteria as potential biofertilisers.

This study was performed to isolate non-rhizobial endophytic bacteria from the root nodules of Glycine max (soybean), Vigna radiata (mung bean) and Vigna unguiculata (cowpea). The bacteria were characterized for plant growth promoting properties such as indole acetic acid production, phosphate and zinc solubilisation, nitrogen fixation and hydrogen cyanide production. Phylogenetic identification was performed using the Neighbour-Joining method on16S rRNA gene sequences. The impact of salt tolerant isolates on some properties of wheat cv. Chamran was evaluated by a completely randomised factorial design. Nine isolates having some characteristics related to plant growth promotion were identified as Staphylococcus hominis 7E, Streptomyces sp. 11E, Bacillus sp. 13E, Acinetobacter sp. 19E, from mung bean, Bacillus endophyticus 1E from cowpea, Staphylococcus hominis 9E, Bacillus endophyticus 14E, Brevundimonas sp. 16E and Kocuria sp. 26E from soybean nodules. Isolates 7E and 19E caused maximum growth inhibition of Fusarium on PDA plate. All isolates were able to grow at salinity levels of mixtures containing up to 400 mM of NaCl, CaCl2 and MgCl2, but their growth was inhibited by increasing salinity level. Only the growth of isolate 14E increased at three levels of salinity compared with control. Some isolates, i.e. 7E, 14E, 19E and 26E had higher colony diameter at 45 °C after 48 h of incubation compared to the growth at 30 and 40 °C. Inoculation of soil with isolate 1E and isolate 26E caused to ameliorate salinity stress in wheat and increased the weight of 1000-grains as compared with non-inoculated treatments.

A critique of widely used normalization software tools and an alternative method to identify reliable reference genes in red clover (Trifolium pratense L.).

Determination of appropriate reference genes is crucial to normalization of gene expression data and prevention of biased results in qRT-PCR studies. This study is the first attempt to systematically compare potential reference genes to detect the most constitutively expressed reference genes for accurate normalization in red clover tissues including leaves, stems and roots. To identify the best-suited reference gene(s) for normalization, several statistical algorithms such as geNorm, BestKeeper and NormFinder have been developed. All these algorithms are based on the key assumption that none of the investigated candidate reference genes show systematic variation in their expression profile across the samples being considered. However, this assumption is likely to be violated in practice. The authors therefore suggest a simple and novel stability index based on the analysis of variance model which is free from the assumption made by the algorithms. We assessed the expression stability of eight candidate reference genes including actin (ACT), glyceraldehyde-3-phosphate-dehydrogenase (GADPH), elongation factor-1alpha (EF-1α), translation initiation factor (EIF-4a), ubiquitin-conjugating enzyme E2 (UBC2), polyubiquitin (UBQ10), sand family protein (SAND) and yellow-leaf-specific protein 8 (YLS8). Our results indicated that UBC2 and UBQ10 ranked as the two most stably expressed genes in leaf tissue. UBC2 and YLS8 were defined as optimal control genes for stem tissue. EIF-4a and UBC2 were found to be the most stable reference gene for root tissue. GAPDH and SAND showed relatively low stability in expression study of red clover. When all tested tissues were considered, we observed that YLS8 and UBC2 showed remarkable stability in their expression level across tissues.