AUTHOR=Yoo Cheol-Min , Quan Li , Blancaflor Elison B.

TITLE=Divergence and Redundancy in CSLD2 and CSLD3 Function During Arabidopsis Thaliana Root Hair and Female Gametophyte Development

JOURNAL=Frontiers in Plant Science

VOLUME=3

YEAR=2012

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2012.00111

DOI=10.3389/fpls.2012.00111

ISSN=1664-462X

ABSTRACT=<p>The <italic>Arabidopsis cellulose synthase-like D</italic> (<italic>CSLD</italic>) <italic>2 and 3</italic> genes are known to function in root hair development. Here, we show that these genes also play a role in female gametophyte development because <italic>csld2 csld3</italic> double mutants were observed to have low seed set that could be traced to defects in female transmission efficiency. Cell biological studies of <italic>csld2 csld3</italic> ovules showed synergid cell degeneration during megagametogenesis and reduced pollen tube penetration during fertilization. Although <italic>CSLD2</italic> and <italic>CSLD3</italic> function redundantly in female gametophyte development, detailed analyses of root hair phenotypes of progeny from genetic crosses between <italic>csld2</italic> and <italic>csld3</italic>, suggest that <italic>CSLD3</italic> might play a more prominent role than <italic>CSLD2</italic> in root hair development. Phylogenetic and gene duplication studies of <italic>CSLD2</italic> and <italic>CSLD3</italic> homologs in <italic>Arabidopsis lyrata</italic>, <italic>Populus</italic>, <italic>Medicago</italic>, maize, and <italic>Physcomitrella</italic> were further performed to investigate the course of evolution for these genes. Our analyses indicate that the ancestor of land plants possibly contained two copies of <italic>CSLD</italic> genes, one of which developed into the <italic>CSLD5</italic> lineage in flowering plants, and the other formed the <italic>CSLD1/2/3/4</italic> clade. In addition, <italic>CSLD2</italic> and <italic>CSLD3</italic> likely originated from a recent genome-wide duplication event explaining their redundancy. Moreover, sliding-window d<italic>N</italic>/d<italic>S</italic> analysis showed that most of the coding regions of <italic>CSLD2</italic> and <italic>CSLD3</italic> have been under strong purifying selection pressure. However, the region that encodes the N-terminus of <italic>CSLD3</italic> has been under relatively relaxed selection pressure as indicated by its high d<italic>N</italic>/d<italic>S</italic> value, suggesting that <italic>CSLD3</italic> might have gained additional functions through more frequent non-synonymous sequence changes at the N-terminus, which could partly explain the more prominent role of <italic>CSLD3</italic> during root hair development compared to <italic>CSLD2</italic>.</p>