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Table of Contents

1 Data Collection & Processing Top

1.1 Gene Information Top

All the gene annotation information for the 70 plant species can be obtained from the URLs provided at the Data Sources tab of this page.

1.2 GO Annotaion Top

GO annotation information was download from the Gene Ontology database (; Release 2010-08-01) [24].

1.3 Small RNA Data Sets Top

♦ Small RNA(sRNA) high-throughput sequencing data sets of each species were obtained from the Gene Expression Omnibus (GEO) database ( [27]. All the sRNA data sets retrieved for this study were summarized in the Statistics page → Small RNA Datasets tab.

♦ SRNA sequences containing incomplete information (such as containing "N") and with length less than 18 or more than 28 were removed for further analysis. For each data set, the filtered sRNA sequences were mapped to all the gene models of the related plant species. All mapping steps were performed using the Bowtie algorithm [33] allowing no mismatches. Besides, for comparison, the normalized abundance of sRNAs from each data set was calculated as RPMs (reads per million), which divided the read number of each sRNA by the total reads from this data set, and multiplied by 106.

1.4 Other Information Top

The transcription factor (TF) information for each species (if available) was retrieved from two TF databases: PlantTFDB (Plant Transcription Factor Database; and PlnTFDB (The Plant Transcription Factor Database;

2 Browser Top

Browser is a quick approach to access your interested information. You can browse your interested species by either "Browse by Species" or "Browse by Classification".

2.1 Browse by Species Top

2.2 Browse by Classification Top

3 Searcher Top

Search can be performed by "Quick Searcher", "Simple Searcher", "Batched Searcher", "Advanced Searcher" or "BLAST Searcher".

3.1 Quick Searcher Top

3.2 Simple Searcher Top

3.4 Batched Searcher Top

3.4 Advanced Searcher Top

3.5 BLAST Searcher Top

4 Viewer Top

4.1 Gene Viewer Top

4.2 NAT Viewer Top

The NAT page largely comprises four main parts, i.e., "NAT Summarization", "Gene Information", "GO Annotation" and "Small RNA Expression".

4.3 Network Viewer Top

Network Viewer supports

5 Association Functions Top

5.1 My Network Top

In "My Network", genes or NAT pairs of interest may be stored temporarily on the server side during the session period and retrieved later. This feature will greatly facilitate users' digging of specific biological network formed by related NAT pairs involved in regulation of the same process. In many pages of the website, there is a button to add selected genes or NAT pairs to "My Network".

5.2 Gene Set Analysis Top

6 Appendix Top

6.1 Useful Hits Top

It's recommended that you use Chrome, Firefox, Safari or Opera to access PlantNATsDB, although IE (Internet Explorer) or Netscape still work well.

6.2 Useful Links Top

See the Useful Links tab of this page.

6.3 Methods Top

See the Methods tab of this page.

6.4 References Top

See the References tab of this page.


Table of Contents

1. Prediction of NAT Pairs Top

Prediction of NAT pairs was performed as previously described [17-18,22]. Specifically, the following criteria were used to identify cis-NATs and trans-NATs, respectively.
  For cis-NATs, they can be grouped into five categories, namely, (i) Divergent (head to head or 5' to 5' overlap); (ii) Convergent (tail to tail or 3' to 3' overlap); (iii) Containing (full overlap); (iv) Nearby head-to-head (5' close to 5') and (v) Nearby tail-to-tail (3' close to 3') according to their relative orientation and degree of overlap (Figure 1A) [28]. If a pair of transcripts was located on opposite strands at adjacent genomic loci, and had at least a 1 nucleotide (nt) overlapping region or their distance on the chromosome was on longer than 100 nts, then they were considered as a cis-NAT pair. In total, 26 plant species were subjected to cis-NAT prediction.
  For trans-NATs, BLASTN (, Release 2.2.20) [29] was used to search for transcript pairs with high sequence complementarity to each other and the following criteria should be satisfied for each transcript pair: (i) If the complementary region identified by BLAST covered more than half the length of either transcript, this transcript pair was designated to be a “high-coverage” (HC) trans-NAT pair; (ii) If the two transcripts had a continuous complementary region longer than 100 nts, they were classified as a “100 nt” pair. Functional trans-NATs should form RNA-RNA duplexes in vivo. We therefore used DINAMelt [30] to verify whether the transcript pairs could melt into RNA-RNA duplexes in the complementary regions in silico. All the trans-NAT pairs based on BLAST search were further used to DINAMelt hybridization validation. The trans-NAT pair was retained if it satisfied: (i) the paired region indentified by DINAMelt should be coincident with the BLAST-based search and (ii) any bubble in the paired region predicted by DINAMelt should be no longer than 10% of the region. For the BLAST-based trans-NAT pairs that contain transcripts longer than 10 Kb, they were not applied to DINAMelt validation due to the heavy computational work. Instead, it was considered as verified trans-NAT, if the paired region identified by BLAST was longer than 10% of its longer transcript.

All the NAT pairs predicted in this study were summarized in the Statistics page → Statistics of NATs tab.

2. Small RNA Analysis Top

Small RNA (sRNA) sequences containing incomplete information (such as containing “N”) and with length less than 18 or more than 28 were removed for further analysis. For each data set, the filtered sRNA sequences were mapped to all the gene models of the related plant species. All mapping steps were performed using the Bowtie algorithm [33] allowing no mismatches. Besides, for comparison, the normalized abundance of sRNAs from each data set was calculated as RPMs (reads per million), which divided the read number of each sRNA by the total reads from this data set, and multiplied by 106.  
  For each NAT, an enrichment score was calculated to evaluate whether sRNAs were enriched in the overlapping region [17-18]. The enrichment score, E, was calculated using the following formula:

in which So = the total normalized abundance of the sRNAs generated from the overlapping region, Lo = the total length of the paired region of the two transcripts of the NATs, Sa = the total normalized abundance of the sRNAs generated from these two transcripts, and La = the total length of the two transcripts. Furthermore, a Pearson's chi-square test (χ2 test) was performed to test whether this enrichment was significant.

3. Gene Set Analysis Top

Statistical tests that have been used for "Gene Set Analysis" to identify enriched GO categories include the Fisher's exact test, the χ2 test, the T test, the binomial test and the hypergeometric test. Here we used the combination of the χ2 test and Fisher's exact test to evaluate the significance of enrichment for GO category.

Input Gene Set Others Total
Interested Term a b a+b
Other Terms c d c+d
Total a+c b+d a+b+c+d

[1]. Fisher's exact test directly calculates the P-value using the following formula:

p = \frac{ \displaystyle{{a+b}\choose{a}} \displaystyle{{c+d}\choose{c}} }{ \displaystyle{{n}\choose{a+c}} } = \frac{(a+b)!(c+d)!(a+c)!(b+d)!}{a!b!c!d!n!}

where  \tbinom nk  is the binomial coefficient and the symbol ! indicates the factorial operator.

[2]. For χ2 test, The value of the test-statistic is

\Chi^2 = \sum_{i=1}^{n} \frac{(O_i - E_i)^2}{E_i} ,


χ2 = Pearson's cumulative test statistic, which asymptotically approaches a χ2 distribution.
Oi = an observed frequency (i.e., a, b, c and d in the above table);
Ei = an expected frequency;
n = the number of cells in the table (i.e., n = 4).

The chi-square statistic can then be used to calculate a P-value by comparing the value of the statistic to a χ2 distribution. The number of degrees of freedom df = 1.

f(x;\,k) = \frac{1}{2^{k/2}\Gamma(k/2)}\,x^{k/2 - 1} e^{-x/2}\, I_{\{x\geq0\}},


k = degrees of freedom df = 1
Γ(k/2) denotes the Gamma function;.

f(x;\,k) = \frac{1}{2^{k/2}\Gamma(k/2)}\,x^{k/2 - 1} e^{-x/2}\, I_{\{x\geq0\}},

For small smaples (i.e., at least one of a, b, c and d is less than 5), PlantNATsDB uses the Fisher's exact test to calculate the P-value to evaluate the significance of enrichment for each category. With large samples, a χ2 test can be used in this situation.


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Data Sources:
ID Scientific name Common Name Type a Release Version Release Date Project Home Download
aly Arabidopsis lyrata Lyrate rockcress Chromosome JGI Araly1 Jul. 22, 2008 Link Link
ath Arabidopsis thaliana Arabidopsis Chromosome TAIR9 Jun. 19, 2009 Link Link
bdi Brachypodium distachyon Purple false brome Chromosome JGI v1.0 8x May 01 2009 Link Link
cpa Carica papaya Papaya Scaffold ASGPB v0.4 Dec 2 Nov. 19, 2008 Link Link
cre Chlamydomonas reinhardtii - Scaffold JGI Chlre4 Jan. 08, 2010 Link Link
csa Cucumis sativus Cucumber Scaffold JGI Cucsa_v1 Jan. 08, 2010 Link Link
fve Fragaria vesca Strawberry Scaffold Version 2 November 16, 2009 Link Link
gma Glycine max Soybean Chromosome JGI Glyma1 Feb. 24, 2010 Link Link
lja Lotus japonicus Lotus Chromosome Lj 1.0 May 18, 2009 Link Link
mac Musa acuminata dwarf banana Chromosome Version 1 Aug. 9,2012 Link Link
mes Manihot esculenta Cassava Scaffold  JGI Cassava1 Nov. 09, 2009 Link Link
mgu Mimulus guttatus Spotted monkey flower Scaffold  JGI Release v1.0 Jan. 20, 2010 Link Link
mpu Micromonas pusilla CCMP1545 - Scaffold JGI Release v2.0 Apr. 3, 2009 Link Link
msp Micromonas sp. RCC299 - Scaffold JGI Release v3.0 Apr. 4, 2009 Link Link
mtr Medicago truncatula Medicago Chromosome Mt 3.0 Oct. 12, 2009 Link Link
olu Ostreococcus lucimarinus CCE9901 - Chromosome JGI Release v2.0 Oct. 27, 2007 Link Link
osi Oryza sativa subsp. indica Rice (indica) Chromosome BGI Release Oct. 28, 2008 Link Link
osj Oryza sativa subsp. japonica Rice (japonica) Chromosome TIGR Rice Release 6.1 Jun. 3, 2009 Link Link
ota Ostreococcus tauri - Chromosome JGI Release v2.0 Apr. 11, 2008 Link Link
ppa Physcomitrella patens Moss Scaffold JGI Phypa1.1 Mar. 22, 2007 Link Link
ppe Prunus persica Peach Scaffold JGI v1.0 May 26, 2009 Link Link
ptr Populus trichocarpa Poplar Chromosome JGI Ptr v2.0 Mar. 16, 2010 Link Link
rco Ricinus communis Castor bean Scaffold TIGR/JCVI Release v0.1 May 22, 2008 Link Link
sbi Sorghum bicolor Sorghum Chromosome JGI Sbi1 Mar. 25, 2008 Link