Premeiotic 24-nt phasiRNAs are present in the Zea genus and unique in biogenesis mechanism and molecular function [Smart-seq2+nanoPARE]. Premeiotic 24-nt phasiRNAs are present in the Zea genus and unique in biogenesis mechanism and molecular function [Smart-seq2+nanoPARE]

Reproductive phasiRNAs are broadly present in angiosperms and play crucial roles in sustaining male fertility. While the premeiotic 21-nt phasiRNAs and meiotic 24-nt phasiRNA pathways have been extensively studied in maize (Zea mays) and rice (Oryza sativa), a third putative category of reproductive phasiRNAs–named premeiotic 24-nt phasiRNAs–have recently been reported in barley (Hordeum vulgare) and wheat (Triticum aestivum). To determine whether premeiotic 24-nt phasiRNAs are also present in maize and related species and begin to characterize their biogenesis and function, we performed a comparative transcriptome and degradome analysis of premeiotic and meiotic anthers from five maize inbred lines and three teosinte species/subspecies. Our data indicate that a substantial subset of the 24-nt phasiRNA loci in maize and teosinte are already highly expressed at premeiotic phase. The premeiotic 24-nt phasiRNAs are similar to meiotic 24-nt phasiRNAs in genomic origin and dependence on DCL5 for biogenesis, but premeiotic 24-nt phasiRNAs are unique in that they are likely (i) not triggered by microRNAs, (ii) not loaded by AGO18 proteins, and (iii) not capable of mediating cis-cleavage. In addition, we also observed a group of premeiotic 24-nt phasiRNAs in rice using previously published data. Together, our results indicate that the premeiotic 24-nt phasiRNAs constitute a unique class of reproductive phasiRNAs and are present more broadly in the grass lineage than previously known. Overall design: Small RNA and degradome profiling of anther materials from five maize inbred lines, a maize mutant, and three teosinte species or subspecies Please note that each processed data file was generated from both Smart-seq2 and nanoPARE samples, and is linked to the corresponding Smart-seq2 sample record. Please note that the *mm in sample titles represents the length of the anther used for the corresponding sample (e.g. 0.4-mm anther for 'B73-0.4mm-rep1' sample), and that the 'ago18HM' and 'ago18HT' represents 'ago18 triple homozygous mutant' and 'ago18 triple heterozygote', respectively.

生殖相位次级小干扰RNA（phasiRNAs）广泛存在于被子植物中，在维持雄性育性方面发挥关键作用。尽管在玉米（Zea mays）和水稻（Oryza sativa）中，减数分裂前21 nt phasiRNAs与减数分裂期24 nt phasiRNAs通路已得到广泛研究，但此前在大麦（Hordeum vulgare）和小麦（Triticum aestivum）中仅报道了第三类推定的生殖phasiRNAs——即减数分裂前24 nt phasiRNAs。为探明减数分裂前24 nt phasiRNAs是否同样存在于玉米及其近缘物种中，并初步解析其生物发生与功能机制，本研究对5个玉米自交系与3个类蜀黍物种/亚种的减数分裂前、减数分裂期花药开展了比较转录组与降解组分析。研究数据显示，玉米与类蜀黍中绝大多数24 nt phasiRNA基因座在减数分裂前阶段即已实现高表达。减数分裂前24 nt phasiRNAs在基因组起源以及依赖DCL5进行生物发生方面与减数分裂期24 nt phasiRNAs高度相似，但二者存在独特差异：减数分裂前24 nt phasiRNAs（i）不受microRNAs触发，（ii）不与AGO18蛋白结合装载，（iii）无法介导顺式切割。此外，本研究借助已发表的公开数据，在水稻中同样检测到一类减数分裂前24 nt phasiRNAs。综合以上结果，本研究证实减数分裂前24 nt phasiRNAs是一类独特的生殖phasiRNAs，且在禾本科植物中的分布范围比此前认知更为广泛。实验设计：对5个玉米自交系、1个玉米突变体以及3个类蜀黍物种/亚种的花药材料开展小RNA与降解组测序分析。请注意：所有处理后的数据文件均由Smart-seq2与nanoPARE两种样本生成，并与对应的Smart-seq2样本记录相关联。请注意：样本名称中的*mm代表对应样本所使用的花药长度（例如样本'B73-0.4mm-rep1'对应的是0.4 mm长度的花药）；'ago18HM'与'ago18HT'分别代表'AGO18三纯合突变体'与'AGO18三杂合子'。