Involvement of Small RNAs in Phosphorus and Sulfur Sensing, Signaling and Stress: Current Update

Abstract

Plants require several essential mineral nutrients for their growth and development. These nutrients are required to maintain physiological processes and structural integrity in plants. The root architecture has evolved to absorb nutrients from soil and transport them to other parts of the plant. Nutrient deficiency affects several physiological and biological processes in plants and leads to reduction in crop productivity and yield. To compensate this adversity, plants have developed adaptive mechanisms to enhance the acquisition, conservation, and mobilization of these nutrients under deficient or adverse conditions. In addition, plants have evolved an intricate nexus of complex signaling cascades, which help in nutrient sensing and uptake as well as to maintain nutrient homeostasis. In recent years, small non-coding RNAs such as micro RNAs (miRNAs) and endogenous small interfering RNAs have emerged as important component in regulating plant stress responses. A set of these small RNAs (sRNAs) have been implicated in regulating various processes involved in nutrient uptake, assimilation, and deficiency. In response to phosphorus (P) and sulphur (S) deficiencies, role of sRNAs, miR395 and miR399, have been identified to be instrumental; however, many more miRNAs might be involved in regulating the plant response to these nutrient stresses. These sRNAs modulate expression of target genes in response to P and S deficiencies and regulate their uptake and utilization for proper growth and development of the plant. This review summarizes the current understanding of uptake, sensing, and signaling of P and S and highlights the regulatory role of sRNAs in adaptive responses to these nutrient stresses in plants.

Similarities and Differences in the Acquisition of Fe and P by Dicot Plants

“…The P leaf concentration of the mutant pho1 is very diminished while in the roots it has concentrations very similar to those of the wild cultivar, which suggests that this mutant has a defect in the loading of P into the xylem [100,[102][103][104]. By contrast, the pho2 mutant accumulates up to three times more P in the aerial part than the wild cultivar, while the root maintains similar levels, or even slightly lower levels than the wild cultivar [43,101,105,106]. The pho2 mutant could either prevent the transport of P through the phloem, from the aerial part to the root, or have some problem in the regulation of P concentration in the leaves [107].…”

“…The pho2 mutant could either prevent the transport of P through the phloem, from the aerial part to the root, or have some problem in the regulation of P concentration in the leaves [107]. More recently, it has been shown that the pho2 mutant lacks a E2 enzyme, which is involved in ubiquitination processes and signaling against P deficiency [104,106]. PHO2 is involved in the degradation of PHO1 via a ubiquitination pathway [106,108].…”

“…More recently, it has been shown that the pho2 mutant lacks a E2 enzyme, which is involved in ubiquitination processes and signaling against P deficiency [104,106]. PHO2 is involved in the degradation of PHO1 via a ubiquitination pathway [106,108]. Micrografting experiments revealed that a pho2 root genotype is sufficient to yield leaf P accumulation [43].…”

“…Buthz et al [119] proposed miRNA399 as the long-distance P-related signal moving through the phloem and involved in the regulation of P deficiency responses in roots. There are models showing the interaction of miRNA399 with the PHO2-E2 enzyme described above, acting together in the signaling against P deficiency and playing an important role in the responses to P deficiency in Arabidopsis thaliana [103,106,108,114].…”

Wheat miRNA TaemiR408 Acts as an Essential Mediator in Plant Tolerance to Pi Deprivation and Salt Stress via Modulating Stress-Associated Physiological Processes

“…MicroRNAs (miRNAs) are 21 to 24 nt-long endogenous non-coding RNAs that widely mediate growth, development, and adaptive response to abiotic stresses via regulating target genes at the posttranscriptional or translation level ( Bonnet et al, 2006 ; Mallory and Vaucheret, 2006 ; Sunkar et al, 2012 ; Ci et al, 2015 ; Sun et al, 2015 ). Numerous miRNA families identified have been confirmed to impact on plant responses to nutrient deprivation and salt stress ( Jones-Rhoades and Bartel, 2004 ; Fujii et al, 2005 ; Chiou et al, 2006 ; Yamasaki et al, 2007 ; Liang et al, 2010 ; Barciszewska-Pacak et al, 2015 ; Khaksefidi et al, 2015 ; Kumar et al, 2017 ). Upon Pi starvation, miR156, miR399, miR778, miR827, and miR2211 of Arabidopsis ( Arabidopsis thaliana ) display an upregulated expression pattern ( Fujii et al, 2005 ).…”