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Sexuality and apomixis are interconnected plant reproductive routes possibly behaving as polyphenic traits under the influence of the environment. In the subtropical grass Paspalum notatum, one of the controllers of apospory, a main component of gametophytic apomixis reproduction, is TRIMETHYLGUANOSINE SYNTHASE 1 (TGS1), a multifunctional gene previously associated with RNA cleavage regulation (including mRNA splicing as well as rRNA and miRNA processing), transcriptional modulation and the establishment of heterochromatin. In particular, the downregulation of TGS1 induces a sexuality decline and the emergence of aposporous-like embryo sacs. The present work was aimed at identifying TGS1 target RNAs expressed during reproductive development of Paspalum notatum. First, we mined available RNA databases originated from spikelets of sexual and apomictic plants, which naturally display a contrasting TGS1 representation, to identify differentially expressed mRNA splice variants and miRNAs. Then, the role of TGS1 in the generation of these particular molecules was investigated in antisense tgs1 sexual lines. We found that CHLOROPHYLL A-B BINDING PROTEIN 1B-21 (LHC Ib-21, a component of the chloroplast light harvesting complex), QUI-GON JINN (QGJ, encoding a MAP3K previously associated with apomixis) and miR2275 (a meiotic 24-nt phasi-RNAs producer) are directly or indirectly targeted by TGS1. Our results point to a coordinated control exercised by signal transduction and siRNA machineries to induce the transition from sexuality to apomixis. [ABSTRACT FROM AUTHOR]

Both types of reproductive phasiRNAs are produced from the same PHAS loci simultaneously In wild strawberry, miR11308 was found to trigger the production of 21-nt and 24-nt phasiRNAs from distinct I PHAS i genes/loci (Pokhrel I et al i ., [4], [5]). These results suggest that reproductive phasiRNAs can be generated from protein-coding genes, and the same I PHAS i gene/locus can be transitive on the production of either 21-nt or 24-nt phasiRNAs, independent of the miRNA trigger. Although there were considerable 24-nt sRNAs generated over the gene, most of these 24-nt sRNAs were not in-phase to the miR2275 cleavage site, indicating this gene is a canonical I 21-PHAS i gene mainly generating 21-nt phasiRNAs. [Extracted from the article]

Sexuality and apomixis are interconnected plant reproductive routes possibly behaving as polyphenic traits under the influence of the environment. In the subtropical grass Paspalum notatum, one of the controllers of apospory, a main component of gametophytic apomixis reproduction, is TRIMETHYLGUANOSINE SYNTHASE 1 (TGS1), a multifunctional gene previously associated with RNA cleavage regulation (including mRNA splicing as well as rRNA and miRNA processing), transcriptional modulation and the establishment of heterochromatin. In particular, the downregulation of TGS1 induces a sexuality decline and the emergence of aposporous-like embryo sacs. The present work was aimed at identifying TGS1 target RNAs expressed during reproductive development of Paspalum notatum. First, we mined available RNA databases originated from spikelets of sexual and apomictic plants, which naturally display a contrasting TGS1 representation, to identify differentially expressed mRNA splice variants and miRNAs. Then, the role of TGS1 in the generation of these particular molecules was investigated in antisense tgs1 sexual lines. We found that CHLOROPHYLL A-B BINDING PROTEIN 1B-21 (LHC Ib-21, a component of the chloroplast light harvesting complex), QUI-GON JINN (QGJ, encoding a MAP3K previously associated with apomixis) and miR2275 (a meiotic 24-nt phasi-RNAs producer) are directly or indirectly targeted by TGS1. Our results point to a coordinated control exercised by signal transduction and siRNA machineries to induce the transition from sexuality to apomixis.

Small RNAs regulate key physiological functions in land plants. Small RNAs can be divided into two categories: microRNAs (miRNAs) and short interfering RNAs (siRNAs); siRNAs are further subdivided into transposon/repetitive region‐localized heterochromatic siRNAs and phased siRNAs (phasiRNAs). PhasiRNAs are produced from the miRNA‐mediated cleavage of a Pol II RNA transcript; the miRNA cleavage site provides a defined starting point from which phasiRNAs are produced in a distinctly phased pattern. 21–22 nucleotide (nt)‐dominated phasiRNA‐producing loci (PHAS) are well represented in all land plants to date. In contrast, 24 nt‐dominated PHAS loci are known to be encoded only in monocots and are generally restricted to male reproductive tissues. Currently, only one miRNA (miR2275) is known to trigger the production of these 24 nt‐dominated PHAS loci. In this study, we use stringent methodologies in order to examine whether or not 24 nt‐dominated PHAS loci also exist in Arabidopsis thaliana. We find that highly expressed heterochromatic siRNAs were consistently misidentified as 24 nt‐dominated PHAS loci using multiple PHAS‐detecting algorithms. We also find that MIR2275 is not found in A. thaliana, and it seems to have been lost in the last common ancestor of Brassicales. Altogether, our research highlights the potential issues with widely used PHAS‐detecting algorithms which may lead to false positives when trying to annotate new PHAS, especially 24 nt‐dominated loci. [ABSTRACT FROM AUTHOR]