AUTHOR=Park Hyo-Young , Lee Hee Tae , Lee Jeong Hwan , Kim Jeong-Kook 

TITLE=Arabidopsis U2AF65 Regulates Flowering Time and the Growth of Pollen Tubes

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00569

DOI=10.3389/fpls.2019.00569

ISSN=1664-462X

ABSTRACT=<p>During pre-mRNA splicing, U2 small nuclear ribonucleoprotein auxiliary factor 65 (U2AF65) interacts with U2AF35 and splicing factor 1 (SF1), allowing for the recognition of the 3′-splice site by the ternary complex. The functional characterization of <italic>U2AF65</italic> homologs has not been performed in <italic>Arabidopsis thaliana</italic> yet. Here, we show that normal plant development, including floral transition, and male gametophyte development, requires two <italic>Arabidopsis U2AF65</italic> isoforms (<italic>AtU2AF65a</italic> and <italic>AtU2AF65b</italic>). Loss-of-function mutants of these two isoforms displayed opposite flowering phenotypes: <italic>atu2af65a</italic> mutants showed late flowering, whereas <italic>atu2af65b</italic> mutants were characterized by slightly early flowering, as compared to that in the wild-type (Col-0) plants. These abnormal flowering phenotypes were well-correlated with the expression patterns of the flowering time genes such as <italic>FLOWERING LOCUS C</italic> (<italic>FLC</italic>) and <italic>FLOWERING LOCUS T</italic> (<italic>FT</italic>). However, the two <italic>atu2af65</italic> mutants did not display any morphological abnormalities or alterations in abiotic stress tests. Double mutation of the <italic>AtU2AF65a</italic> and <italic>AtU2AF65b</italic> genes resulted in non-viable seeds due to defective male gametophyte. <italic>In vitro</italic> pollen germination test revealed that mutations in both <italic>AtU2AF65a</italic> and <italic>AtU2AF65b</italic> genes significantly impaired pollen tube growth. Collectively, our findings suggest that two protein isoforms of AtU2AF65 are differentially involved in regulating flowering time and display a redundant role in pollen tube growth.</p>