Abstract
MicroRNAs (miRNAs) are important regulators of plant growth and development. Previously, we identified a group of conserved and novel miRNA families from soybean (Glycine max) roots. Many of these miRNAs are specifically induced during soybean-Bradyrhizobium japonicum interactions. Here, we examined the gene expression levels of six families of novel miRNAs and investigated their functions in nodule development. We used northern-blot analyses to study the tissue specificity and time course of miRNA expression. Transgenic expression of miR482, miR1512, and miR1515 led to significant increases of nodule numbers, while root length, lateral root density, and the number of nodule primordia were not altered in all tested miRNA lines. We also found differential expression of these miRNAs in nonnodulating and supernodulating soybean mutants. The expression levels of 22 predicted target genes regulated by six novel miRNAs were studied by real-time polymerase chain reaction and quantitative real-time polymerase chain reaction. These results suggested that miRNAs play important roles in soybean nodule development.
Highlights
IntroductionWe identified a group of conserved and novel miRNA families from soybean (Glycine max) roots
MicroRNAs are important regulators of plant growth and development
Two conserved miRNAs have been studied in M. truncatula for their functions during nodulation. miR169 was shown to regulate MtHAP2-1, which altered nodule development (Combier et al, 2006), while overexpression of miR166 reduced the number of symbiotic nodules and lateral roots (Boualem et al, 2008)
Summary
We identified a group of conserved and novel miRNA families from soybean (Glycine max) roots. We examined the gene expression levels of six families of novel miRNAs and investigated their functions in nodule development. The expression levels of 22 predicted target genes regulated by six novel miRNAs were studied by real-time polymerase chain reaction and quantitative real-time polymerase chain reaction. These results suggested that miRNAs play important roles in soybean nodule development. The conserved legume miRNAs, such as miR399 from P. vulgaris, was shown to negatively regulate the ubiquitin E2 conjugase during phosphorus starvation responses (Valdes-Lopez et al, 2008) This function was consistent with miR399’s function reported in Arabidopsis. Two conserved miRNAs have been studied in M. truncatula for their functions during nodulation. miR169 was shown to regulate MtHAP2-1, which altered nodule development (Combier et al, 2006), while overexpression of miR166 reduced the number of symbiotic nodules and lateral roots (Boualem et al, 2008)
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