Abstract
Root growth and the architecture of the root system in Arabidopsis are largely determined by root meristematic activity. Legume roots show strong developmental plasticity in response to both abiotic and biotic stimuli, including symbiotic rhizobia. However, a global analysis of gene regulation in the root meristem of soybean plants is lacking. In this study, we performed a global analysis of the small RNA transcriptome of root tips from soybean seedlings grown under normal and salt stress conditions. In total, 71 miRNA candidates, including known and novel variants of 59 miRNA families, were identified. We found 66 salt-responsive miRNAs in the soybean root meristem; among them, 22 are novel miRNAs. Interestingly, we found auxin-responsive cis-elements in the promoters of many salt-responsive miRNAs, implying that these miRNAs may be regulated by auxin and auxin signaling plays a key role in regulating the plasticity of the miRNAome and root development in soybean. A functional analysis of miR399, a salt-responsive miRNA in the root meristem, indicates the crucial role of this miRNA in modulating soybean root developmental plasticity. Our data provide novel insight into the miRNAome-mediated regulatory mechanism in soybean root growth under salt stress.
Highlights
The root is an important organ that supports the aerial parts of plants, and absorbs water and nutrients for plant growth and survival
The root apical meristem (RAM) is localized at the root tip and harbors a stem cell niche that serves as the source of new cells for continuous apical root growth involving iterative processes of cell division, elongation, and differentiation (Dinneny and Benfey, 2008; Perilli et al, 2012)
To investigate the responses of roots to salt stress, we performed a systematic study of soybean root development
Summary
The root is an important organ that supports the aerial parts of plants, and absorbs water and nutrients for plant growth and survival. The growth rate and architecture of roots are dynamically regulated by internal and external cues, and they are largely determined by the activity of the root apical meristem (RAM) (De Tullio et al, 2010; Ubeda-Tomas and Bennett, 2010; Petricka et al, 2012). The fate of root meristem cells is determined by both developmental and environmental cues in Arabidopsis plants. An auxin-mediated regulatory pathway has been identified; in this pathway, auxin regulates the establishment of the stem cell niche and activity of the RAM through PLETHORA1/2, an AP2/EREBP family transcription factor (Ding and Friml, 2010). It was shown that the salt-induced reduction in RAM activity is mediated by auxin and auxin signaling in Arabidopsis (Liu et al, 2015). The molecular mechanism through which RAM activity is modulated in response to salt stress remains largely unknown
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