Dynamics and functions of small interfering RNAs in germline cells

小干扰rna （sirna）在生殖细胞功能调控中发挥着重要作用。在开花植物中，21- 22nt sirna参与了从精子伴侣细胞（称为营养细胞）到沉默精子转座子的运动。然而，非细胞自主信号的性质和沉默机制一直存在争议。最近，我的宿主实验室发现，在拟南芥雄性种系中，减数细胞护理细胞（称为绒毡层）产生的24-nt sirna驱动DNA甲基化重编程，从而调节基因并抑制转座子。这些绒毡层sirna足以在精子中形成整个新生甲基组，然而，由于绒毡层和精子之间缺乏细胞质连接，尚不清楚这是如何实现的。我的初步工作表明，在种系发育过程中，siRNA转运有两波：第一波是从绒毡层细胞到减数细胞，第二波是从营养细胞到精子。21-22和24 nt sirna都被认为是通过与细胞特异性Argonaute蛋白相互作用进行转运，分别在转录后和转录基因沉默中发挥重要作用。结合细胞生物学、分子遗传学、单细胞基因组学、表观遗传学和生物化学方法，我将通过以下研究来验证这些创新假设并阐明潜在的分子机制：Obj.1) siRNA的生物发生和转运如何介导雄性种系DNA甲基化；Obj.2) 21-22 nt siRNA在雄性种系发育过程中的起源和功能；Obj.3)细胞特异性Argonauts在种系siRNA通路中的核心作用。我的研究将通过揭示生殖细胞中siRNA的生物发生、运输和沉默功能的复杂动力学，为我们对植物种系和遗传的理解开辟新的视野。这种深入的知识也将允许细胞和位点特异性甲基化工程作物改良。

Small interfering RNAs (siRNAs) play essential roles in regulating germline functions. In flowering plants, 21-22 nt siRNAs have been implicated in the movement from sperm companion cells (called vegetative cells) to silence sperm transposons. However, the nature and silencing mechanism of the non-cell autonomous signal have remained controversial. Recently, my host lab discovered that 24-nt siRNAs produced by meiocyte nurse cells (called tapetum) drive DNA methylation reprogramming in the Arabidopsis male germline, thereby regulating genes and suppressing transposons. These tapetum siRNAs are sufficient to shape the entire de novo methylome in sperm, however, it is unclear how this is achieved given the absence of cytoplasmic connections between the tapetum and sperm.My preliminary work indicates that there are two waves of siRNA transport during germline development: the first wave from tapetal cells to meiocytes, and the second from vegetative cells to sperm. 21-22and 24 nt siRNAs are both suggested to be transported, playing important roles in post-transcriptional and transcriptional gene silencing, respectively, via interacting with cell-specific Argonaute proteins. Using a combination of cell biology, molecular genetics, single-cell-type genomics, epigenetics and biochemistry approaches, I will test these innovative hypotheses and elucidate the underlying molecular mechanisms by investigating: Obj.1) how siRNA biogenesis and transport mediate DNA methylation in the male germline, Obj.2) the origin and function of 21-22 nt siRNAs during male germline development, and Obj.3) the central role of cell-specific Argonauts in germline siRNA pathways. My investigations will open a new horizon in our understanding of plant germlines and heredity by revealing the intricate dynamics of siRNA biogenesis, transport, and silencing functions in the germ cells. This in-depth knowledge will also allow cell- and site-specific engineering of methylation for crop improvement.