Control Roots Research Articles

Genome-Wide Identification of miRNAs Responsive to Drought in Peach (Prunus persica) by High-Throughput Deep Sequencing

Peach (Prunus persica L.) is one of the most important worldwide fresh fruits. Since fruit growth largely depends on adequate water supply, drought stress is considered as the most important abiotic stress limiting fleshy fruit production and quality in peach. Plant responses to drought stress are regulated both at transcriptional and post-transcriptional level. As post-transcriptional gene regulators, miRNAs (miRNAs) are small (19–25 nucleotides in length), endogenous, non-coding RNAs. Recent studies indicate that miRNAs are involved in plant responses to drought. Therefore, Illumina deep sequencing technology was used for genome-wide identification of miRNAs and their expression profile in response to drought in peach. In this study, four sRNA libraries were constructed from leaf control (LC), leaf stress (LS), root control (RC) and root stress (RS) samples. We identified a total of 531, 471, 535 and 487 known mature miRNAs in LC, LS, RC and RS libraries, respectively. The expression level of 262 (104 up-regulated, 158 down-regulated) of the 453 miRNAs changed significantly in leaf tissue, whereas 368 (221 up-regulated, 147 down-regulated) of the 465 miRNAs had expression levels that changed significantly in root tissue upon drought stress. Additionally, a total of 197, 221, 238 and 265 novel miRNA precursor candidates were identified from LC, LS, RC and RS libraries, respectively. Target transcripts (137 for LC, 133 for LS, 148 for RC and 153 for RS) generated significant Gene Ontology (GO) terms related to DNA binding and catalytic activites. Genome-wide miRNA expression analysis of peach by deep sequencing approach helped to expand our understanding of miRNA function in response to drought stress in peach and Rosaceae. A set of differentially expressed miRNAs could pave the way for developing new strategies to alleviate the adverse effects of drought stress on plant growth and development.

Root and root-lignin degradation in a Norway spruce stand: Effects of long-term nitrogen addition

Mass loss, degradation of lignin and the qualitative change of the organic C structures of spruce root litter (2 – 5 mm in diameter) in O-horizon were studied for a period of 6 years (1995 – 2001) in a Norway spruce stand with a current deposition of 13 kg N and 12 kg S ha−1 yr−1. The stand was fertilized annually by addition of 100 kg N and 114 kg S ha−1 (NS). Litterbags, acid detergent lignin (ADL), CuO-oxidation as well as 13C-NMR were used for measurements of mass loss, lignin concentration, degradation of lignin and changes of the organic C structures, respectively. The roots originating from the NS-treated plots lost 20% of their mass in the first year while in control (CON) plots the corresponding value was 10%. After 1879 days of decomposition the fertilized roots had a cumulative mass loss of 54% compared with the CON roots of 44%. The C/N ratios were significantly lower in the NS roots (35) than in the CON roots (59) after 1879 days of decomposition. The initial concentrations of ADL were 34.7 and 36.6 in CON and NS roots and increased to 50 and 56%, respectively, after 1879 days. Using CuO-oxidation method the degree of lignin degradation was significantly higher in the NS than CON roots after 853 days while 13C NMR method showed no change. Our results indicate that CuO-oxidation and solid-state 13C NMR methods give a qualitative measure of lignin decomposition, while the litterbag and ADL methods allow us to quantify mass loss and lignin concentration, respectively. It is concluded that the mass loss of root litter in fertilized plots is higher than needle litter decomposition in the same stand and the higher nitrogen concentration increases the lignin degradation.