PT  - JOURNAL ARTICLE
AU  - Takashi Tsuchimatsu
AU  - Hiroyuki Kakui
AU  - Misako Yamazaki
AU  - Cindy Marona
AU  - Hiroki Tsutsui
AU  - Afif Hedhly
AU  - Dazhe Meng
AU  - Yutaka Sato
AU  - Thomas Städler
AU  - Ueli Grossniklaus
AU  - Masahiro M. Kanaoka
AU  - Michael Lenhard
AU  - Magnus Nordborg
AU  - Kentaro K. Shimizu
TI  - Adaptive Reduction of Male Gamete Number in a Selfing Species
AID  - 10.1101/272757
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 272757
4099  - http://biorxiv.org/content/early/2018/02/28/272757.short
4100  - http://biorxiv.org/content/early/2018/02/28/272757.full
AB  - The number of male gametes produced is critical for reproductive success and varies greatly between and within species1–3. Evolutionary reduction of male gamete production has been widely reported in plants as a hallmark of the selfing syndrome, as well as in humans. Such a reduction may simply represent deleterious decay4–7, but evolutionary theory predicts that breeding systems could act as a major selective force on male gamete number: while large numbers of sperm should be produced in highly promiscuous species because of male–male gamete competition1, reduced sperm numbers may be advantageous at lower outcrossing rates because of the cost of gamete production. Here we used genome-wide association study (GWAS) to show a signature of polygenic selection on pollen number in the predominantly selfing plant Arabidopsis thaliana. The top associations with pollen number were significantly more strongly enriched for signatures of selection than those for ovule number and 107 phenotypes analyzed previously, indicating polygenic selection8. Underlying the strongest association, responsible for 20% of total pollen number variation, we identified the gene REDUCED POLLEN NUMBER 1 affecting cell proliferation in the male germ line. We validated its subtle but causal allelic effects using a quantitative complementation test with CRISPR-Cas9-generated null mutants in a nonstandard wild accession. Our results support polygenic adaptation underlying reduced male gamete numbers.