Mutants in the imprinted PICKLE RELATED 2 gene suppress seed abortion of fertilization independent seed class mutants and paternal excess interploidy crosses in Arabidopsis.
Endosperm cellularization is essential for embryo development and viable seed formation. Loss of function of the FERTILIZATION INDEPENDENT SEED (FIS) class Polycomb genes, which mediate trimethylation of histone H3 lysine27 (H3K27me3), as well as imbalanced contributions of parental genomes interrupt this process. The causes of the failure of cellularization are poorly understood. In this study we identified PICKLE RELATED 2 (PKR2) mutations which suppress seed abortion in fis1/mea by restoring endosperm cellularization. PKR2, a paternally expressed imprinted gene (PEG), encodes a CHD3 chromatin remodeler. PKR2 is specifically expressed in syncytial endosperm and its maternal copy is repressed by FIS1. Seed abortion in a paternal genome excess interploidy cross was also partly suppressed by pkr2. Simultaneous mutations in PKR2 and another PEG, ADMETOS (ADM), additively rescue the seed abortion in fis1 and in the interploidy cross, suggesting that PKR2 and ADM modulate endosperm cellularization independently and reproductive isolation between plants of different ploidy is established by imprinted genes. Genes upregulated in fis1 and downregulated in the presence of pkr2 are enriched in glycosyl-hydrolyzing activity, while genes downregulated in fis1 and upregulated in the presence of pkr2 are enriched with microtubule motor activity, consistent with the cellularization patterns in fis1 and the suppressor line. The antagonistic functions of FIS1 and PKR2 in modulating endosperm development are similar to those of PICKLE (PKL) and CURLY LEAF (CLF), which antagonistically regulate root meristem activity. Our results provide further insights into the function of imprinted genes in endosperm development and reproductive isolation.
Rice Research Institute, Sichuan Agricultural University, Wenjiang, Chengdu, Sichuan, 611130, China.
Fang
F
Huang
Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture and Food, PO Box 1700, ACT, 2601, Australia.
Qian-Hao
QH
Zhu
Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture and Food, PO Box 1700, ACT, 2601, Australia.
Anyu
A
Zhu
Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture and Food, PO Box 1700, ACT, 2601, Australia.
Xiaoba
X
Wu
School of Life Science and Technology, Xinjiang University, Urumqi, 830046, China.
Liqiong
L
Xie
Rice Research Institute, Sichuan Agricultural University, Wenjiang, Chengdu, Sichuan, 611130, China.
Xianjun
X
Wu
Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture and Food, PO Box 1700, ACT, 2601, Australia.
Chris
C
Helliwell
HKG-Agro, Shamshernagare, Bangladesh.
Abed
A
Chaudhury
Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture and Food, PO Box 1700, ACT, 2601, Australia.
E Jean
EJ
Finnegan
Commonwealth Scientific and Industrial Research Organization (CSIRO), Agriculture and Food, PO Box 1700, ACT, 2601, Australia.
Ming
M
Luo
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D056625:Endosperm / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; C104597:CURLY LEAF protein, Arabidopsis; D018398:Homeodomain Proteins; D014157:Transcription Factors; C402442:AT2G25170 protein, Arabidopsis; D004265:DNA Helicases

FIS
; cellularization; endosperm; interploidy cross; reproductive isolation; speciation