Reproductive phasiRNAs regulate reprogramming of gene expression and meiotic progression in rice

Abstract

Plant spermatogenesis is a complex process that directly affects crop breeding. A rapid change in gene abundance occurs at early meiosis prophase, when gene regulation is selective. However, how these genes are regulated remains unknown. Here, we show that rice reproductive phasiRNAs are essential for the elimination of a specific set of RNAs during meiotic prophase I. These phasiRNAs cleave target mRNAs in a regulatory manner such that one phasiRNA can target more than one gene, and/or a single gene can be targeted by more than one phasiRNA to efficiently silence target genes. Our investigation of phasiRNA-knockdown and PHAS-edited transgenic plants demonstrates that phasiRNAs and their nucleotide variations are required for meiosis progression and fertility. This study highlights the importance of reproductive phasiRNAs for the reprogramming of gene expression during meiotic progression and establishes a basis for future studies on the roles of phasiRNAs with a goal of crop improvement.

Rice MEL2 regulates the timing of meiotic transition as a component of cytoplasmic RNA granules

“…DAZAP1 is potentially associated with stress granules in puromycin-treated iPS cells [42]. Furthermore, when the Recent works showed that the gene expression profile changes dramatically at the early meiotic prophase I in maize PMCs [49], and the rice reproductive phased siRNAs (phasiRNAs) associated with MEL1 Argonaute regulate the reprogramming of gene expression through the direct RNA cleavage [50,51]. In addition to phasiRNAs-MEL1 mediated mRNA degradation, some MEL2 granules may be involved in the decay process working alongside P-bodies to remove a subset of transcripts that are dispensable for progression through meiosis.…”

Oxygen, secreted proteins and small RNAs: mobile elements that govern anther development

“…One study in pummelo predicted and verified targets in trans with gene ontologies of broad terms but also including PCD and pollen development (Fang et al 2020). By now, two pioneering study in rice meiocytes finally found indeed RNA degradation of target genes of reproductive 21nt-phasiRNAs (Jiang et al 2020;Zhang et al 2020c). In rice meiocytes, target genes were enriched for carbohydrate biosynthesis and metabolism, and also included OsDMC1B, a meiotic gene (Jiang et al 2020).…”

“…Another study gained insight on genes targeted for degradation in rice anthers through degradome data from whole rice spikelets of WT and of mutants in MEL1, the rice AGO5 which binds phasiRNA. Intriguingly, many RLKs were identified as phasiRNA target genes, among them MSP1 (Zhang et al 2020c). This re-defines part of the reproductive phasiRNAs as tasiRNAs, with specific target genes with roles and/or high abundance in meiosis and anther development (Dukowic-Schulze et al 2014;Wang et al 2016).…”

“…The second part needs further examination. • Q4: What are the functions of genes targeted by phasi RNAs for degradation, as identified now in rice (Jiang et al 2020;Zhang et al 2020c)? Are there further targets in other cells, at other times?…”

Exploiting Genic Male Sterility in Rice: From Molecular Dissection to Breeding Applications

“…The availability or generation of a stable male sterile line is the prerequisite to produce high-quality hybrids. Over the years, EGMS lines have been broadly used for two-line systems of hybrid breeding because of (1) availability of germplasm resources and (2) reversibility of fertility via the manipulation of environmental factors ( Chen and Liu, 2014 ; Xue et al, 2018 ; Zhu et al, 2020 ; Zhang Y. et al, 2020 ). On the other hand, abrupt environmental fluctuations have always posed a serious threat for their wider applications.…”