Project description:In maize, 24-nt phased, secondary small interfering RNAs (phasiRNAs) are abundant in meiotic stage anthers, but their distribution and functions are not precisely known. Using laser capture microdissection (LCM), we analyzed tapetal cells, meiocytes, and other somatic cells at several stages of anther development to establish the timing of 24-PHAS precursor transcripts and the 24-nt phasiRNA products. This dataset includes 24-nt phasiRNA part of data. 24-nt phasiRNAs are found to accumulate in all cell types, with the highest levels in meiocytes, followed by tapetum.
Project description:In maize, 24-nt phased, secondary small interfering RNAs (phasiRNAs) are abundant in meiotic stage anthers, but their distribution and functions are not precisely known. Using laser capture microdissection we analyzed tapetal cells, meiocytes, and other somatic cells at several stages of anther development to establish the timing of 24-PHAS precursor transcripts and the 24-nt phasiRNA products. By integrating RNA and small RNA (sRNA) profiling plus single-molecule and sRNA FISH (smFISH or sRNA-FISH) spatial detection, we demonstrate that the tapetum is the primary site of 24-PHAS precursor and Dcl5 transcripts and the resulting 24-nt phasiRNAs. Interestingly, 24-nt phasiRNAs accumulate in all cell types, with the highest levels in meiocytes, followed by tapetum. Our data support the conclusion that 24-nt phasiRNAs are mobile from tapetum to meiocytes and to other somatic cells. We discuss possible roles for 24-nt phasiRNAs in anther cell types.
Project description:The maize ocl4 mutants showed differing levels of male sterility, which seems correlating with the quantity of 21-nt phasiRNA remaining during pre-meiotic stage. In this case, sRNA and transcriptome was profiled and compared in this study, showed that OCL4 and 21-nt phasiRNAs are dispensable for male fertility in maize anthers.
Project description:Anthers are the male reproductive floral organs, but loss of the 24-nt class of phased small-interfering RNAs (phasiRNAs) may confer temperature-sensitive male sterility in maize. 24-nt phasiRNAs from 176 loci are abundant coordinately in fertile maize anthers after the last periclinal divisions are complete, all four wall layers are formed, and meiosis has initiated in the pollen mother cells. In this study, we found male sterile maize ms23, ms32, and bhlh122 mutants with various degrees of tapetal defects lack 24-PHAS mRNA precursors and 24-nt phasiRNAs, which were not affected in another male sterile mutant, bhlh51. Transcription from most of 24-PHAS loci depends on bHLH122 while bHLH122 and Dcl5 transcription depends on both Ms23 and Ms32. Multiple lines of evidence suggest that 24-nt phasiRNAs biogenesis is primarily controlled at multiple layers by MS23 and MS32, with distinctive action on 24-PHAS transcription by bHLH122, creating a transcription factor cascade in maize tapetal cells.
Project description:In grasses, phased small interfering RNAs (phasiRNAs), 21- or 24-nucleotide (nt) in length, are predominantly expressed in anthers and regulate male fertility. However, their targets and mode of action on the targets remain unknown. Here we profile phasiRNA expression in premeiotic and meiotic spikelets as well as in purified male meiocytes at early prophase I, tetrads and microspores in rice. We show that 21-nt phasiRNAs are most abundant in meiocytes at early prophase I while 24-nt phasiRNAs are more abundant in tetrads and microspores. By performing highly sensitive degradome sequencing, we find that 21-nt phasiRNAs direct target mRNA cleavage in male germ cells, especially in meiocytes at early prophase I. The target genes in early prophase I meiocytes show an enrichment for carbohydrate biosynthetic and metabolic pathways. Our study provides strong evidence that 21-nt phasiRNAs act in a target-cleavage mode and may facilitate the progression of meiosis by fine-tuning carbohydrate biosynthesis and metabolism in male germ cells.
Project description:Purpose: To study pre-meiotic (21-nt) and meiotic (24-nt) phasiRNA pathways in non-grass monocots Methods: Anthers were dissected using a 2 mm stage micrometer in a stereo microscope, and immediately frozen in liquid nitrogen until total RNA isolation was performed. Small RNA, mRNA libraries were generated using short-read (Illumina) and Single Molecule Real Time SMRT (PacBio) sequencing approaches. Stages were assigned based on the morphology of archesporial (AR) and tapetal cells of A. officinalis (Asparagus) anthers.
Project description:As a key member of the grass-specific subclade of argonaute proteins, AGO18b protein has been proposed to bind 24-nt meiotic phasiRNAs based on their co-expression in tapetal and meiotic cells. Here we show that expression of in maize tassels is strictly induced by developmental stages. Interestingly, reduced expression of AGO18b in both Mutator-mediated (ago18b::mum) and RNAi mutants leads to an increase in plant height and tassel length, suggesting its non-meiotic function as a negative regulator of SAM/IM maintenance. During the premiotic stage, AGO18b primarily binds to 21-nt phasiRNAs with 5’-uridine and less binds to 24-nt phasiRNAs with 5’-adenosine, coincident with its enrichment of miR2275 required for the 24-nt phasiRNA production. MiR166a, the negative regulator of SAM, is mostly enriched among AGO18b-bound miRNAs, implicating a novel negative regulator of IM. We suggest that AGO18b regulates maize tassel development via both phasiRNAs and miRNA pathways.
Project description:Purpose: To study pre-meiotic (21-nt) and meiotic (24-nt) phasiRNA pathways in non-grass monocots Methods: Anthers were dissected using a 2 mm stage micrometer in a stereo microscope, and immediately frozen in liquid nitrogen until total RNA isolation was performed. Small RNA, mRNA libraries were generated using short-read (Illumina) and Single Molecule Real Time SMRT (PacBio) sequencing approaches. Stages were assigned based on the morphology of archesporial (AR) and tapetal cells of H. lilioasphodelus (Daylily) anthers.
Project description:Small RNAs play important roles during plant development by regulating transcript levels of target mRNAs, maintaining genome integrity, and reinforcing DNA methylation. Dicer-like 5 (Dcl5) is proposed to be responsible for precise slicing to generate diverse 24-nt phased, secondary small interfering RNAs (phasiRNAs), which are exceptionally abundant in meiotic anthers of maize, rice, and other grasses 1. Importance and functions of these phasiRNAs remain unclear. Here we used the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) Cas9 system to mutate Dcl5. We report that dcl5 mutants have few or no 24-nt phasiRNAs, develop short anthers and defective tapetal cells, and exhibit temperature-sensitive male fertility. We propose that DCL5 and 24-nt phasiRNAs are critical for fertility under growth regimes for optimal yield.