Regulatory short RNAs: A decade's tale for manipulating salt tolerance in plants

Brassinolide improves the tolerance of Malus hupehensis to alkaline stress

Malus hupehensis is one of the most widely used apple rootstocks in china but is severely damaged by alkaline soil. Alkaline stress can cause more serious harmful effects on apple plants than salt stress because it also induces high pH stress except for ion toxicity, osmotic stress, and oxidative damage. Brassinolide (BL) plays important roles in plant responses to salt stress. However, its role and function mechanism in apple plants in response to alkaline stress has never been reported. This study showed that applying exogenous 0.2 mg/L BL significantly enhanced the resistance of M. hupehensis seedlings to alkaline stress. The main functional mechanisms were also explored. First, exogenous BL could decrease the rhizosphere pH and promote Ca²⁺ and Mg²⁺ absorption by regulating malic acid and citric acid contents and increasing H⁺ excretion. Second, exogenous BL could alleviate ion toxicity caused by alkaline stress through enhancing Na⁺ efflux and inhibiting K⁺ expel and vacuole compartmentalization. Last, exogenous BL could balance osmotic stress by accumulating proline and reduce oxidative damage through increasing the activities of antioxidant enzymes and antioxidants contents. This study provides an important theoretical basis for further analyzing the mechanism of exogenous BL in improving alkaline tolerance of apple plants.

Transcriptome dynamics uncovers long non-coding RNAs response to salinity stress in Chenopodium quinoa

Chenopodium quinoa is a crop with outstanding tolerance to saline soil, but long non-coding RNAs (LncRNAs) expression profile driven by salt stress in quinoa has rarely been observed yet. Based on the high-quality quinoa reference genome and high-throughput RNA sequencing (RNA-seq), genome-wide identification of LncRNAs was performed, and their dynamic response under salt stress was then investigated. In total, 153,751 high-confidence LncRNAs were discovered and dispersed intensively in chromosomes. Expression profile analysis demonstrated significant differences between LncRNAs and coding RNAs. Under salt stress conditions, 4,460 differentially expressed LncRNAs were discovered, of which only 54 were differentially expressed at all the stress time points. Besides, strongly significantly correlation was observed between salt-responsive LncRNAs and their closest neighboring genes (r = 0.346, p-value < 2.2e-16). Furthermore, a weighted co-expression network was then constructed to infer the potential biological functions of LncRNAs. Seven modules were significantly correlated with salt treatments, resulting in 210 hub genes, including 22 transcription factors and 70 LncRNAs. These results indicated that LncRNAs might interact with transcription factors to respond to salinity stress. Gene ontology enrichment of the coding genes of these modules showed that they were highly related to regulating metabolic processes, biological regulation and response to stress. This study is the genome-wide analysis of the LncRNAs responding to salt stress in quinoa. The findings will provide a solid framework for further functional research of salt responsive LncRNAs, contributing to quinoa genetic improvement.

miRNAomic Approach to Plant Nitrogen Starvation

Nitrogen (N) is one of the indispensable nutrients required by plants for their growth, development, and survival. Being a limited nutrient, it is mostly supplied exogenously to the plants, to maintain quality and productivity. The increased use of N fertilizers is associated with high-cost inputs and negative environmental consequences, which necessitates the development of nitrogen-use-efficient plants for sustainable agriculture. Understanding the regulatory mechanisms underlying N metabolism in plants under low N is one of the prerequisites for the development of nitrogen-use-efficient plants. One of the important and recently discovered groups of regulatory molecules acting at the posttranscriptional and translational levels are microRNAs (miRNAs). miRNAs are known to play critical roles in the regulation of gene expression in plants under different stress conditions including N stress. Several classes of miRNAs associated with N metabolism have been identified so far. These nitrogen-responsive miRNAs may provide a platform for a better understanding of the regulation of N metabolism and pave a way for the development of genotypes for better N utilization. The current review presents a brief outline of miRNAs and their regulatory role in N metabolism.