Correction: Expansion of Capsicum annum fruit is linked to dynamic tissue-specific differential expression of miRNA and siRNA profiles.

[This corrects the article DOI: 10.1371/journal.pone.0200207.].

Expansion of Capsicum annuum fruit is linked to dynamic tissue-specific differential expression of miRNA and siRNA profiles.

Small regulatory RNAs, such as microRNAs (miRNAs) and small interfering RNAs (siRNAs) have emerged as important transcriptional and post-transcriptional regulators controlling a wide variety of physiological processes including fruit development. Data are, however, limited for their potential roles in developmental processes determining economically important traits of crops. The current study aimed to discover and characterize differentially expressed miRNAs and siRNAs in sweet pepper (Capsicum annuum) during fruit expansion. High-throughput sequencing was employed to determine the small regulatory RNA expression profiles in various fruit tissues, such as placenta, seed, and flesh at 28 and 40 days after anthesis. Comparative differential expression analyses of conserved, already described and our newly predicted pepper-specific miRNAs revealed that fruit expansion is accompanied by an increasing level of miRNA-mediated regulation of gene expression. Accordingly, ARGONAUTE1 protein, the primary executor of miRNA-mediated regulation, continuously accumulated to an extremely high level in the flesh. We also identified numerous pepper-specific, heterochromatin-associated 24-nt siRNAs (hetsiRNAs) which were extremely abundant in the seeds, as well as 21-nt and 24-nt phased siRNAs (phasiRNAs) that were expressed mainly in the placenta and the seeds. This work provides comprehensive tissue-specific miRNA and siRNA expression landscape for a developing pepper fruit. We identified several novel, abundantly expressing tissue- and pepper-specific small regulatory RNA species. Our data show that fruit expansion is associated with extensive changes in sRNA abundance, raising the possibility that manipulation of sRNA pathways may be employed to improve the quality and quantity of the pepper fruit.

Non-targeted effects of virus-induced gene silencing vectors on host endogenous gene expression.

Virus-induced gene silencing (VIGS) uses recombinant viruses to study gene function; however, the effect of the virus vector itself on the gene expression of the host is not always considered. In our work, we investigated non-targeted gene expression changes of the host in order to see how often these changes appear. Effects of various VIGS vector infections were analysed by monitoring gene expression levels of housekeeping genes by Northern blot analysis in four different hosts. We found that non-targeted changes happens very often. More importantly, these non-targeted effects can cause drastic changes in the gene-expression pattern of host genes that are usually used as references in these studies. We have also found that in a tobacco rattle virus (TRV)-based VIGS, the presence of foreign sequences in the cloning site of the vector can also have a non-targeted effect, and even the use of an internal control can lead to unpredicted changes. Our results show that although VIGS is a very powerful technique, the VIGS vector, as a pathogen of the host, can cause unwanted changes in its gene-expression pattern, highlighting the importance of careful selection of both the genes to be tested and those to be used as references in the planned experiments.