Qian Weiqiang's research group has made new progress in the expression of nitrogen starvation regulated transposons in Arabidopsis

In organisms, transposable elements (TEs) are silenced by a variety of epigenetic mechanisms, including DNA methylation, inhibitory histone modifications, and advanced chromatin structures
.
Nitrogen is one
of the main limiting factors for plant growth and agricultural productivity.
Although the gene regulatory network in plants in response to nitrogen hunger has been extensively studied, the effect of nitrogen hunger on the regulation of transposon elements is unclear
.

JIPB recently published a research paper
by Qian Weiqiang's research group of the School of Modern Agriculture of Peking University entitled "Nitrogen starvation induces genome-wide activation of transposon elements in Arabidopsis" 。 Using a forward genetic approach, the study identified glutamate synthase (GLU1) that affects transcriptional level gene silencing, and combined with a series of molecular biology and genetic experiments, explored the effect of
nitrogen starvation on activated transposon expression.

Figure 1 Glutamate metabolism regulates transposon silencing

The researchers found that mutations in GLU1 in Arabidopsis thaliana caused the expression of the foreign gene d35S-LUC in the context of idm1-14 to be upregulated
.
Moreover, the dual mutants of glutamate synthase have a significantly higher effect on endogenous transposon expression than monomutants
.
The addition of glutamic acid exogenously can restore to some extent the degree
of upregulation of transposon expression in glu1-204 glt1-1 mutants.
Succinate semialdehyde dehydromutants (ssadh-5) and glu1-204 glt1-1, located downstream of glutamate metabolism and involved in GABA metabolism, regulate some common sites (Figure 1
).
On the other hand, nitrogen starvation can significantly upregulate the expression
of foreign genes in the context of YJ and idm1-14.
Moreover, nitrogen-starved WT and glu1-204 glt1-1 can jointly activate the expression level
of some transposons.
The sequencing and analysis of the transcriptome also showed that nitrogen starvation activates the expression
of a large number of transposons in the Arabidopsis genome.
The analysis results of genome-wide methylation data showed that the change of transposon expression level induced by nitrogen starvation did not depend on the change of DNA methylation level of the transposon itself, and the expression analysis of multiple mutants further confirmed this conclusion
.

In summary, the study explored the effect of nitrogen starvation on transposon expression levels across the genome of Arabidopsis thaliana and showed that nitrogen metabolism may not regulate transposon expression levels without affecting their DNA methylation levels
and higher-level structures of chromatin.

Dr.
Yue Wang and doctoral student Liu Yi of Peking University are the first authors of the paper, and researcher Qian Weiqiang is the corresponding author
of the paper.
Dr.
Qu Shaofeng also made important contributions to this work, and Professor Fan Liumin of Peking University also participated in the research work
.
The research was funded
by the National Natural Science Foundation of China and the National Key Research and Development Program.