Regulatory long non-coding RNAs in root growth and development

As sessile organisms, plants have evolved sophisticated mechanisms of gene regulation to cope with changing environments. Among them, long non-coding RNAs (lncRNAs) are a class of RNAs regulating gene expression at both transcriptional and post-transcriptional levels. They are highly responsive to environmental cues or developmental processes and are generally involved in fine-tuning plant responses to these signals. Roots, in addition to anchoring the plant to the soil, allow it to absorb the major part of its mineral nutrients and water. Furthermore, roots directly sense environmental constraints such as mineral nutrient availability and abiotic or biotic stresses and dynamically adapt their growth and architecture. Here, we review the role of lncRNAs in the control of root growth and development. In particular, we highlight their action in fine-tuning primary root growth and the development of root lateral organs, such as lateral roots and symbiotic nodules. Lastly, we report their involvement in plant response to stresses and the regulation of nutrient assimilation and homeostasis, two processes leading to the modification of root architecture. LncRNAs could become interesting targets in plant breeding programs to subtly acclimate crops to coming environmental changes.

Study of rice root distribution patterns for breeding of drought tolerant varieties

Root growth and development is one of the morphological characters which related to drought tolerant traits. This study aims to evaluate the root distribution pattern of 30 rice genotypes to support the breeding of drought tolerant varieties. The research was conducted in ICRR greenhouse in Sukamandi, Subang, Indonesia from October to December 2015. Thirty rice genotypes, consisting of cultivars, promising lines (prior to be released as new varieties), and check varieties, were arranged using randomized complete block design with three replications. Seed were planted in mini pots containing a mixture of sand and soil media with a concave sieve at the top. The filter is divided into three zones, namely upper (1), middle (2), and lower (3). The pot was placed in a plastic box filled with water to maintain the humidity. The results showed that Mekongga had the number of tillers, the number of fresh leaves, the number of roots in zone 1, and the total number of roots significantly higher than the best check variety, Salumpikit. In this study, it was found that the amount of metaxylem between genotypes was different. Salumpikit has the most metaxylem among other genotypes. Further research is expected to be carried out both in drought and optimum condition as a control to see the correlation between root architecture with drought tolerance in the field.

An Optical Clearing Technique to Visualize Internal Root Structure

BackgroundRoots play an important role in the foraging and uptake of nutrients and water from soil to support sessile plant growth. Research on root growth and development in plants is very limited due to the thickness and opacity of roots. We developed a tissue clearing technique that enables visualization of crop internal root structure.ResultsThe application of methyl salicylate reduced the time taken for root clearing and accelerated the dye permeation into the tissue; the whole procedure for root clearing was performed within 3 days. We applied our technique on the roots of monocotyledonous plants, such as rice (Oryza sativa L.), wheat (Triticum aestivum L.), and maize (Zea mays L.), and dicotyledonous plants, such as rape (Brassica napus L. var oleifera), tomato (Solanum lycopersicum), and soybean (Glycine max (Linn.) Merr.), and obtained clear root structure. It not only shortens the time for root tissue clearing but also keeps the cell structure of intact roots. The transparent sample can be preserved for more than one year without any structural deformation.ConclusionsOur technique can create a 3-D reconstruction of the entire root structure. In summary, this method is a useful tool for visualizing the structures of thick root tissues and will be a valuable tool for research on root growth and development in plants.

Biochar Improves Root Growth of Sapium sebiferum (L.) Roxb. Container Seedlings

Background: The faulty development of the root system is a major threat that affects the survival rate of container seedlings of Sapium sebiferum in the transplanting and reforestation processes. The current study was conducted to determine the impact of biochar on the root growth and development of S. sebiferum container seedlings. Methods: Varied concentrations (1%, 3%, and 5%) of straw and bamboo biochar were applied in six groups, whereas the control group (CK) was only treated with matrix. Results: The treatment with 3% straw biochar (C2) proved to be the most effective soil conditioner for cultivating S. sebiferum seedlings. Moreover, C2 increased seedling height (58.92%); ground diameter (33.86%, biomass of the over-ground part (12.73 g), the underground part (7.48 g), and the fibrous part (0.076 g) compared to the CK (control). Conclusions: Biochar not only improved the root morphology by developing primary lateral roots, but it also accelerated the assimilation of N from the matrix to indirectly facilitate stem growth through enhancing NR activity. The change in root growth strategy contributed to the growth in S. sebiferum seedlings, thereby improving the survival rate during transplanting and reforestation.

Response of Root Growth and Development to Nitrogen and Potassium Deficiency as well as microRNA-Mediated Mechanism in Peanut (Arachis hypogaea L.)

The mechanism of miRNA-mediated root growth and development in response to nutrient deficiency in peanut (Arachis hypogaea L.) is still unclear. In the present study, we found that both nitrogen (N) and potassium (K) deficiency resulted in a significant reduction in plant growth, as indicated by the significantly decreased dry weight of both shoot and root tissues under N or K deficiency. Both N and K deficiency significantly reduced the root length, root surface area, root volume, root vitality, and weakened root respiration, as indicated by the reduced O2 consuming rate. N deficiency significantly decreased primary root length and lateral root number, which might be associated with the upregulation of miR160, miR167, miR393, and miR396, and the downregulation of AFB3 and GRF. The primary and lateral root responses to K deficiency were opposite to that of the N deficiency condition. The upregulated miR156, miR390, NAC4, ARF2, and AFB3, and the downregulated miR160, miR164, miR393, and SPL10 may have contributed to the growth of primary roots and lateral roots under K deficiency. Overall, roots responded differently to the N or K deficiency stresses in peanuts, potentially due to the miRNA-mediated pathway and mechanism.