RT Journal
A1 Li, Chenxin
A1 Xu, Hengping
A1 Fu, Fang-Fang
A1 Russell, Scott D.
A1 Sundaresan, Venkatesan
A1 Gent, Jonathan I.
T1 Genome-wide redistribution of 24-nt siRNAs in rice gametes
JF Genome Research 
JO Genome Research 
YR 2020 
FD February 01 
VO 30 
IS 2 
SP 173 
OP 184 
DO 10.1101/gr.253674.119 
UL http://genome.cshlp.org/content/30/2/173.abstract 
AB Gametes constitute a critical stage of the plant life cycle during which the genome undergoes reprogramming in preparation for embryogenesis. Here, we examined genome-wide distributions of small RNAs in the sperm and egg cells of rice. We found that 24-nt siRNAs, which are a hallmark of RNA-directed DNA methylation (RdDM) in plants, were depleted from heterochromatin boundaries in both gametes relative to vegetative tissues, reminiscent of siRNA patterns in DDM1-type nucleosome remodeler mutants. In sperm cells, 24-nt siRNAs were spread across heterochromatic regions, while in egg cells, 24-nt siRNAs were concentrated at a smaller number of heterochromatic loci throughout the genome, especially at loci which also produced siRNAs in other tissues. In both gametes, patterns of CHH methylation, typically a strong indicator of RdDM, were similar to vegetative tissues, although lower in magnitude. These findings indicate that the small RNA transcriptome undergoes large-scale redistribution in both male and female gametes, which is not correlated with recruitment of DNA methyltransferases in gametes and suggestive of unexplored regulatory activities of gamete small RNAs.