Abstract
BackgroundAGO (Argonaute) protein participates in plant developmental processes and virus defense as a core element of transcriptional regulator or/and post-transcriptional regulator in RNA induced silencing complex (RISC), which is guided by small RNAs to repress target genes expression. Previously, it was revealed that 15 putative AGO genes in tomato genome.ResultsIn present study, out of 15 detected SlAGO genes, only SlAGO4C and SlAGO15 couldn’t be detected in roots, stems, leaves, buds, flowers and fruit of tomato by 30 cycles of PCR. SlAGO7 could be detected in early stage of fruit (-2 dpa, 0 dpa and 4 dpa), but it was significantly down-regulated in fruit collected on the 6 days post anthesis. Moreover, SlAGO5 could only be detected in reproductive tissues and SlAGO4D was specifically detected in fruit. According to blast result with miRNA database, three SlAGO genes harbored complementary sequences to miR168 (SlAGO1A and SlAGO1B) or miR403 (SlAGO2A). 5′ RACE (Rapid amplification of cDNA ends) mapping was used to detect the 3′ cleavage products of SlAGO mRNAs. In addition, subcellular localization of SlAGO proteins was detected. Our results showed that most SlAGO proteins localized to nucleus and cytoplasm. Importantly, nuclear membrane localization of AGO proteins was observed. Furthermore, mutated miR168 complementary site of SlAGO1A resulted in expanded localization of SlAGO1A, indicating that miR168 regulated localization of SlAGO1A.ConclusionsOur results contribute to demonstration of potential roles of these newly isolated AGO family in tomato developmental processes and proved the conserved relationships between AGO genes and miRNAs in tomato, which might play important roles in tomato development and virus defense.
Highlights
AGO (Argonaute) protein participates in plant developmental processes and virus defense as a core element of transcriptional regulator or/and post-transcriptional regulator in RNA induced silencing complex (RISC), which is guided by small RNAs to repress target genes expression
MicroRNA, small interfering RNAs, PIWI-interacting RNAs, scanRNAs and 21URNAs were produced, and these types of small RNAs were associated with different AGO family members including AGO, PIWI and group 3 proteins to act biological functions [6,7,8,9]
SlAGO family genes in tomato locate in chromosome 1 (SlAGO4A, SlAGO7, SlAGO4D), chromosome 2 (SlAGO2A, SlAGO3, SlAGO genes ranged from bp (SlAGO2B)), chromosome 3 (SlAGO1B, SlAGO15), chromosome 6 (SlAGO 1A, SlAGO4C, SlAGO4B, SlAGO5), chromosome 7 (SlAGO6), chromosome 9 (SlAGO10A), chromosome 12 (SlAGO10), but none of the SlAGO genes distribute in chromosome 4, 5, 8, 10 and 11. (Figure 1 and Additional file 1)
Summary
AGO (Argonaute) protein participates in plant developmental processes and virus defense as a core element of transcriptional regulator or/and post-transcriptional regulator in RNA induced silencing complex (RISC), which is guided by small RNAs to repress target genes expression. Guided by miRNAs, AGO proteins recognize target genes at complementary sites to repress gene translation by cleaving target mRNAs binding to cap structure of mRNAs, and in some cases to repress gene transcription by RNA directed DNA methylation [10,11,12,13,14]. Each AGO protein performs biological functions differently by binding to small RNAs and direct transcriptional regulation or/and post-transcriptional regulation of target genes. AGO1-like proteins cleaved target mRNA or/and repressed coding process directed by miRNAs [18]. AGO2-like proteins fought against virus infection guided by siRNAs generated from double strand virus RNAs, which were synthesized by RNA-dependent RNA polymerase (RdRP) using viral RNA as templates [19]
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