8 publications mentioning mtr-MIR171c

Open access articles that are associated with the species Medicago truncatula and mention the gene name MIR171c. Click the [+] symbols to view sentences that include the gene name, or the word cloud on the right for a summary.

1

In M. trunctula, one member of miR171 family (miR171h) regulates AM symbiosis by directly targeting the NSP2 gene (Lauressergues et al., 2012; Hofferek et al., 2014).

The up-regulation of miR171 and miR171g in tomato revealed by this study, therefore suggests that a conserved miRNA family was adopted by different plant lineages to regulate AM symbiosis.

The direct regulation of miR171 on NPS2 has recently been validated in vitro and miR171h can directly influence the AM in M. trunctula (Lauressergues et al., 2012; Hofferek et al., 2014).

Cleavage of miR171 on scarecrow-like proteins is one of the earliest evidenced miRNA-target interactions in plants (Llave et al., 2002b).

We identified six AM symbiosis responsive known miRNAs in tomato and revealed that two of the miR171 family members, miR171 and miR171g in tomato, are also capable of targeting NSP2.

Besides NSP2, miR171 and miR171g have two other common targets, Solyc08g078800.1.1 and Solyc01g090950.2.1.

Our data revealed that two members of miR171 family (miR171 and miR171g) were predicted to target an NSP2 ortholog with low mismatch penalties and also supported by the degradome.

Another AM symbiosis responsive miR171 member is miR171e-5p, which has different predicted target gene with the above miR171 members.

Besides NSP2, tomato miR171 and miR171g have another two common targets, Solyc08g078800.1.1 and Solyc01g090950.2.1, which are both annotated as scarecrow-like proteins.

This further suggested that some miR171 members might function as common regulators of AM symbiosis in different plant lineages.

Therefore, whether the regulation of scarecrow-like proteins by miR171 members has a role in AM symbiosis is interesting.

Interestingly, tomato miR171 and miR171g actually share high sequence identity with a miRNA named Mtr-miR171h, which has been reported to regulate AM symbiosis in M. truncatula (Lauressergues et al., 2012; Hofferek et al., 2014).

These results suggest that miR171 family may serve as a common regulator of AM symbiosis.

MiR171 and miR397 are associated with nodule infection and the nitrogen-fixing ability of Lotus japonicus (De Luis et al., 2012).

Five miRNA families (miR399, miR156, miR166, miR171, and miR172) had more than 10 members, and miR156 family, the largest family, had 23 members.

Three of them were miR171 family members, including miR171, miR171g, and miR171i.

Both of the two genes are annotated as scarecrow-like proteins and their cleavage by miR171 has been validated previously (Huang et al., 2015).

2

Both MtGRAS1 and 31 exhibited highest expression in nodules, while Pv-miR171 genes (Pv-miR171-1 and Pv-miR171-2) showed the lowest expression in this tissue.

The expression pattern of Pv-miR171 genes were negatively correlated with their targets.

MicroRNA171c -targeted SCL6-II, SCL6-III, and SCL6-IV genes regulate shoot branching in Arabidopsis.

Furthermore, the triple scl6 mutants and overexpressing miR171 showed similar pleiotropic phenotypes [34].

Putative Pv-miR171 genes and their target MtGRAS genes.

The targets of miR171 were predicted in silico using the website (http://plantgrn.

Overexpressing miR171 had pleiotropic phenotypes including plant height, flowering time, leaf architecture, phase transitions and floral meristem determinacy [34– 36].

0185439.g006 Fig 6Putative Pv-miR171 genes and their target MtGRAS genes.

Three HAM homologs in Arabidopsis (SCL6-II, SCL6-III, and SCL6-IV) were post-transcriptionally regulated by miRNA171 and play vital roles in the proliferation of meristematic cells [37– 39].

In Arabidopsis, three GRAS members in the HAM subfamily were post-transcriptionally regulated by miR171 (AtSCL6, 22, and 27).

The microRNA171(miR171) family is one of the most ancient and well conserved miRNA families which have diverse roles in plant development, such as flowering, meristem identity, and phase transition [32, 33].

Furthermore, three Arabidopsis GRAS genes (SCL6, 22, and 27) in the HAM subfamily are post-transcriptionally regulated by miR171.

Rice osa-miR171c Mediates Phase Change from Vegetative to Reproductive Development and Shoot Apical Meristem Maintenance by Repressing Four OsHAM Transcription Factors.

Here, the two closest homologs of SCL6, MtGRAS1 and MtGRAS31, were identified as having a putative binding site for miR171 (Fig 6A).

The Pv-miR171 genes were identified based on the homology searching stem-loop sequence of osa-miR171, which obtained from the website of miRbase (http://www.

In buds, MtGRAS1 and 31 accumulated the least transcript, but the transcript of Pv-miR171 genes, especially Pv-miR171-1, was the highest among different tissues(Fig 6B).

Two Pv-miR171 genes were detected in the Medicago genome.

Interestingly, in the present study, the two closest homologs of AtSCL6 (MtGRAS1 and 31) were found to have a putative binding site for miR171.

3

Thus, cytokinin signaling may have a dual mode for regulating NSP2 expression: it can directly activate NSP2 transiently and then repress its expression through activation of miR171 expression (Figure 1).

The regulatory mechanism for NSP2 expression is currently a vibrant area of research in plant–microbe interactions; recent evidence indicates that expression of NSP2 is negatively regulated by microRNA 171 (miR171; De Luis et al., 2012; Lauressergues et al., 2012).

Expression of miR171 is induced not only during nodule development but also by cytokinin in an MtCRE1 -dependent manner, and the expression pattern is negatively correlated with that of NSP2 (Ariel et al., 2012).

4

Additionally, a recent study employing deep sequencing of Lotus japonicus nodules revealed a non-canonical miR171 isoform, related to Medicago miR171h, which targets LjNSP2 [[36]].

Furthermore, a recent study from De Luis et al. [[36]] in L. japonicus identified a homologue of miR171h, lja-miR171c, in determinate root nodules, which similarly targets LjNSP2.

Interestingly, a novel member of the miRNA171 family, miR171h, was shown to target NSP2 [[30],[31]].

Previous attempts to overexpress miR171h and miR171c in M. truncatula and L. japonicus failed, which could be explained by the use of the 35S promoter, which seems to be diminished in arbuscule containing cells [[52]] and root nodules [[53],[54]] and thus might lead to a variation of the results.

Data from Arabidopsis and Rapeseed did not imply that the miR171 family is regulated by phosphate and nitrogen availability [[45]].

It is possible that the phosphate dependent regulation of a miR171 family member is dependent of the ability to undergo root endosymbiosis, because the miR171h isoform is only present in AMS capable plants [[27],[32]].

Whether additional miR171 family members are phosphate responsive in these plant species is not known.

5

In both species, the specific miR171 isoforms studied were able to cleave the target transcript NSP2, a TF involved in NOD factor signaling.

The common function of miR171 isoforms in nodulation and mycorrhization reinforces the idea that nodule development may have evolved from AM fungi interactions though a diversification and specialization process.

More recently, a novel isoform of miR171 was discovered in M. truncatula and L. japonicus (Devers et al., 2011; Bazin et al., 2012; De Luis et al., 2012), that repress a key actor of symbiotic signaling, NSP2 (Nodulation Signaling Pathway 2, a GRAS TF).

Finally, the role of miR171 in legumes, first suggested by Devers et al. (2011), emerged through three different reports.

In L. japonicus, De Luis et al. (2012) showed that, similarly to miR397, the miR171c isoform accumulated in inoculated snf mutants and that this miRNA variant was associated to nodule establishment and maintenance but not organogenesis.

Lauressergues et al. (2012) and De Luis et al. (2012) showed that the miR171h and miR171c variants are fundamental to establish symbiotic mycorrhization and nodulation in M. truncatula and L. japonicus, respectively.

Further analyses of the miR171 family using both miRBase and comparative genomics (Bazin et al., 2012) revealed that this isoform is also present in non-legume species, such as Populus trichocarpa (ptc-miR171) and Citrus sinensis (csi-miR171b).

6

Instead of the conserved SCARECROW-like GRAS TF targets of miR171, these miR171 variants recognize a different but related NSP2 GRAS TF involved in molecular regulation associated with the common symbiosis (sym) pathway [22– 24].

In addition, lja-miR171c and mtr-miR171h specifically regulate NSP2, which encodes a key GRAS TF involved in both RL and AM symbioses [22- 24].

These miR171 variants thus may have coevolved with NSP2 genes in plants undergoing endosymbioses.

Recently, De Luis et al. [22] and Lauressergues et al. [23] showed that specific variants of miR171 control RL symbiosis in Lotus japonicus and AM fungal colonization in M. truncatula, respectively.

In fact, few families contained more than five variants and the greatest complexity was found in three conserved families (Additional file 6: Figure S2; Additional file 2: Table S2a), miR156 and miR169 (6 variants each) as well as miR171 (7 variants).

7

Conversely, 10 members belonging to 6 miRNA families, i. e., miR164, miR169, miR171, miR396, miR398 and miR1510, were down-regulated in response to drought stress (Figure 3b and 3c).

In the present study, we found that the known or predicted targets of miR164, miR169, miR171, miR396, miR1510 and miR5558 were either transcription factors or F-box proteins (Table 3, 4).

8

We found homologs of known miRNA target genes for several conserved M. truncatula miRNAs, such as SBP for miR156, NAC for miR160, AGO1 for miR168, bZIP for miR165, GRAS for miR171, AP2 for miR172 and low affinity sulphur transporter for miR395.