Differential Expression of MicroRNAs During Root Formation in Taxus Chinensis Var. mairei Cultivars.

MicroRNAs (miRNAs) have been shown to play key roles in the regulation of plant growth and development by modifying the expression of their target genes. However, the influence of miRNAs on root formation and development in woody plants, such as Taxus chinensis, remains largely unknown. In the current study, we explored the phytohormone-response and nutrition-response miRNA expression profiles during T. chinensis rooting by quantitative real-time PCR (qPCR). We identified six phytohormone-response miRNAs, namely, miR164a, miR165, miR167a, miR171b, miR319, and miR391, and eight nutrition-response miRNAs, namely, miR169b, miR395a, miR399c, miR408, miR826, miR827, miR857, and miR2111a, that were differentially expressed at different rooting phases of T. chinensis. Using northern blot analysis of the putative target genes of these miRNAs, we detected the relative gene expression changes of the target genes. Taken together, our results suggest that miRNAs are involved in root formation of T. chinensis and that miRNAs may play important regulatory roles in primary root, crown root, and root hair formation by targeting phytohormone and/or nutrition response genes in T. chinensis. For the first time, these results expand our understanding of the molecular mechanisms of plant root formation and development in a conifer species.

Molecular and Functional Diversity of RNA Editing in Plant Mitochondria.

RNA editing is a fundamental biochemical process relating to the modification of nucleotides in messenger RNAs of functional genes in cells. RNA editing leads to re-establishment of conserved amino acid residues for functional proteins in nuclei, chloroplasts, and mitochondria. Identification of RNA editing factors that contributes to target site recognition increases our understanding of RNA editing mechanisms. Significant progress has been made in recent years in RNA editing studies for both animal and plant cells. RNA editing in nuclei and mitochondria of animal cells and in chloroplast of plant cells has been extensively documented and reviewed. RNA editing has been also extensively documented on plant mitochondria. However, functional diversity of RNA editing factors in plant mitochondria is not overviewed. Here, we review the biological significance of RNA editing, recent progress on the molecular mechanisms of RNA editing process, and function diversity of editing factors in plant mitochondrial research. We will focus on: (1) pentatricopeptide repeat proteins in Arabidopsis and in crop plants; (2) the progress of RNA editing process in plant mitochondria; (3) RNA editing-related RNA splicing; (4) RNA editing associated flower development; (5) RNA editing modulated male sterile; (6) RNA editing-regulated cell signaling; and (7) RNA editing involving abiotic stress. Advances described in this review will be valuable in expanding our understanding in RNA editing. The diverse functions of RNA editing in plant mitochondria will shed light on the investigation of molecular mechanisms that underlies plant development and abiotic stress tolerance.

Overexpression of Zinc Finger Transcription Factor ZAT6 Enhances Salt Tolerance.

The purpose of the present investigation is to examine the function of the C2H2-type zinc finger transcription factor of Arabidopsis thaliana 6 (ZAT6) in salt stress tolerance in cells of rice (Oryza sativa L.), cotton (Gossypium hirsutum L.) and slash pine (Pinus elliottii Engelm.). Cells of O. sativa, G. hirsutum, and P. elliottii overexpressing ZAT6 were generated using Agrobacterium-mediated genetic transformation. Molecular and functional analysis of transgenic cell lines demonstrate that overexpression of ZAT6 increased tolerance to salt stress by decreasing lipid peroxidation and increasing the content of abscisic acid (ABA) and GA8, as well as enhancing the activities of antioxidant enzymes such as ascorbate peroxidise (APOX), catalase (CAT), glutathione reductase (GR), and superoxide dismutase (SOD). In rice cells, ZAT6 also increased expression of Ca2+-dependent protein kinase genes OsCPK9 and OsCPK25 by 5-7 fold under NaCl stress. Altogether, our results suggest that overexpression of ZAT6 enhanced salt stress tolerance by increasing antioxidant enzyme activity, hormone content and expression of Ca2+-dependent protein kinase in transgenic cell lines of different plant species.