Genome-wide identification of Thellungiella salsuginea microRNAs with putative roles in the salt stress response.
BACKGROUND
MicroRNAs are key regulators of plant growth and development with important roles in environmental adaptation. The microRNAs from the halophyte species Thellungiella salsuginea (salt cress), which exhibits extreme salt stress tolerance, remain to be investigated. The sequenced genome of T. salsuginea and the availability of high-throughput sequencing technology enabled us to discover the conserved and novel miRNAs in this plant species. It is interesting to identify the microRNAs from T. salsuginea genome wide and study their roles in salt stress response.


RESULTS
In this study, two T. salsuginea small RNA libraries were constructed and sequenced using Solexa technology. We identified 109 miRNAs that had previously been reported in other plant species. A total of 137 novel miRNA candidates were identified, among which the miR* sequence of 26 miRNAs was detected. In addition, 143 and 425 target mRNAs were predicted for the previously identified and Thellungiella-specific miRNAs, respectively. A quarter of these putative targets encode transcription factors. Furthermore, numerous signaling factor encoding genes, defense-related genes, and transporter encoding genes were amongst the identified targets, some of which were shown to be important for salt tolerance. Cleavage sites of seven target genes were validated by 5' RACE, and some of the miRNAs were confirmed by qRT-PCR analysis. The expression levels of 26 known miRNAs in the roots and leaves of plants subjected to NaCl treatment were determined by Affymetrix microarray analysis. The expression of most tested miRNA families was up- or down-regulated upon NaCl treatment. Differential response patterns between the leaves and roots were observed for these miRNAs.


CONCLUSIONS
Our results indicated that diverse set of miRNAs of T. salsuginea were responsive to salt stress and could play an important role in the salt stress response.
College of Life Sciences, Shandong Normal University, Jinan 250014, PR China. xingjunw@hotmail.com.
Quan
Q
Zhang
Chuanzhi
C
Zhao
Ming
M
Li
Wei
W
Sun
Yan
Y
Liu
Han
H
Xia
Mingnan
M
Sun
Aiqin
A
Li
Changsheng
C
Li
Shuzhen
S
Zhao
Lei
L
Hou
Jean-François
JF
Picimbon
Xingjun
X
Wang
Yanxiu
Y
Zhao
D001483:Base Sequence; D019607:Brassicaceae / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D015723:Gene Library; D017343:Genes, Plant / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D020411:Oligonucleotide Array Sequence Analysis; D018749:RNA, Plant / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics*
D035683:MicroRNAs; D018749:RNA, Plant; D012965:Sodium Chloride