Zm401, a short‐open reading‐frame mRNA or noncoding RNA, is essential for tapetum and microspore development and can regulate the floret formation in maize

Abstract

In flowering plants, pollen formation depends on the differentiation and interaction of two cell types in the anther: the reproductive cells, called microsporocytes, and somatic cells that form the tapetum. Previously, we cloned a pollen specific gene, zm401, from a cDNA library generated from the mature pollen of Zea mays. Expression of partial cDNA of zm401 in maize and ectopic expression of zm401 in tobacco suggested it may play a role in anther development. Here we present the expression and functional characterization of this pollen specific gene in maize. Zm401 is expressed primarily in the anthers (tapetal cells as well as microspores) in a developmentally regulated manner. That is, it is expressed from floret forming stage, increasing in concentration up to mature pollen. Knockdown of zm401 significantly affected the expression of ZmMADS2, MZm3-3, and ZmC5, critical genes for pollen development; led to aberrant development of the microspore and tapetum, and finally male-sterility. Zm401 possesses highly conserved sequences and evolutionary conserved stable RNA secondary structure in monocotyledon. These data show that zm401 could be one of the key growth regulators in anther development, and functions as a short-open reading-frame mRNA (sORF mRNA) and/or noncoding RNA (ncRNA).

The Conserved Chimeric Transcript UPGRADE2 Is Associated with Unreduced Pollen Formation and Is Exclusively Found in Apomictic Boechera Species

“…Given its chimeric structure, the novel lncRNA BspUPG2 could have attained neofunctionalization in the context of apomeiosis for pollen development through a number of mechanisms (Kaessmann, 2010), similar to the lncRNAs BcMF11 from Brassica campestris (Song et al, , 2013 and Zm401 in maize (Zea mays; Ma et al, 2008). BspUPG2 could conceivably have a regulatory function via a homology-dependent gene-silencing (HDGS) mechanism (for review, see Meyer and Saedler, 1996), such as posttranscriptional gene silencing of related Figure 8.…”

The Role of Long Non-coding RNAs in Abiotic Stress Tolerance in Plants

“…Other putative lncRNAs such as CsM10 from cucumber (Cho et al 2005 ) and zm401 from maize (Dai et al 2004 ;Ma et al 2008 ) have been found to be expressed in somatic tapetal cells, developing male gametophyte and might function in male reproductive development. Transgenic plants with downregulated zm401 transcripts exhibited abnormal development of the tapetum, leading to the production of infertile pollen grains (Grant-Downton and Rodriguez-Enriquez 2012 ).…”

Long non-coding RNA-mediated mechanisms independent of the RNAi pathway in animals and plants

“…Forward and reverse genetic studies deduced a function for Zm401 in regulating the expression of critical genes necessary for pollen development including ZmMADS2, MZm3-3 and ZmC5. 112,113 MZm3-3 was upregulated in Zm401 mutants while ZmMADS2 and ZmC5 were both downregulated. 113 Overexpression of Zm401 severely affects pollen development due to abnormal tassels and degenerate anthers.…”

“…112,113 MZm3-3 was upregulated in Zm401 mutants while ZmMADS2 and ZmC5 were both downregulated. 113 Overexpression of Zm401 severely affects pollen development due to abnormal tassels and degenerate anthers. 112 How this lncRNA can mediate the downregulation of certain genes but the upregulation of others is intriguing and remains to be elucidated.…”