Potassium accumulation and translocation a mongrice genotypes in relation to internal potassium use efficiency(IKUE)

Abiotie stresses including potassium deficiency are limitingfactors for increasing rice yield.Nine rice genotypes(Oryza Sativa L.,indica)differing in sensitivity to low Kstress selected from 200 volume-solution screening wereused in this study to examine accumulation and transloca-tion ofK.The powdery-muddy paddy soil tested contained 30.6mg·kgavailable K(1 N NHAcO extracted),1.92%

Ancestral function but divergent epigenetic regulation of HAIKU2 reveals routes of seed developmental evolution

Evolution is driven by various mechanisms.A directional increase in the embryo to endosperm ratio is an evolutionary trend within the angiosperms.The endosperm constitutes a major portion of the seed volume in Poales and some dicots.However,in other dicots such as Arabidopsis and soybean,the endosperm proliferates early,followed by embryo growth to replace the endosperm.The Arabidopsis leucine-rich repeat receptor protein kinase AtHAIKU2(AtIKU2)is a key regulator of early endosperm proliferation.In this study,we found that IKU2s from Brachypodium,rice,and soybean can complement the abnormal seed developmental phenotype of Atiku2,while AtIKU2 also rescues the defective endosperm proliferation in the Brachypodium BdIKU2 knockout mutant seeds.AtIKU2 and soybean GmIKU2 are actively expressed a few days after fertilization.Thereafter,expression of AtIKU2 is suppressed by the FIS-PRC2 complex-mediated H3K27me3.The soybean GmIKU2 locus is also enriched with H3K27me3 marks.The histone methyltransferase AtMEA is unique to Brassicaceae,but one GmSWN in soybean plays a similar role in seed development as AtMEA.By contrast,the BdIKU2 and rice OsIKU2 loci are continuously expressed and are devoid of H3K27me3 marks.Taken together,these results suggest that IKU2 genes retain an ancestral function,but the duration of their expression that is controlled by PRC2-mediated epigenetic silencing contributes to silenced or persistent endosperm proliferation in different species.Our study reveals an epigenetic mechanism that drives the development of vastly different seed ontogenies.

Two MADS-box proteins,AGL9 and AGL15,recruit the FIS-PRC2 complex to trigger the phase transition from endosperm proliferation to embryo development in Arabidopsis

Spatiotemporal regulation of gene expression by polycomb repressive complex 2(PRc2)is critical for animal and plant development.The Arabidopsis fertilization independent seed(FIS)-PRC2 complex functions specifically during plant reproduction from gametogenesis to seed development.After a double fertilization event,triploid endosperm proliferates early,followed by the growth of a diploid embryo,which replaces the endosperm in Arabidopsis and many dicots.Key genes critical for endosperm proliferation such as IKkU2 and MINI3 are activated after fertilization.Here we report that two MADS-box AGAMOUS-LIKE(AGL)proteins associate with the key endosperm proliferation loci and recruit the FIS-PRC2 repressive complex at 4-5 days after pollination(DAP).Interestingly,AGL9 and AGL15 only accumulate toward the end of endosperm proliferation at 4-5 DAP and promote the deposition of H3K27me3 marks at key endosperm proliferation loci.Disruption of AGL9 and AGL15 or overexpression of AGL9 or AGL15 significantly influence endosperm proliferation and cellularization.Genome-wide analysis with cleavage Under Targets and tagmentation(CUT&Tag)sequencing and RNA sequencing revealed the landscape of endosperm H3K27me3 marks and gene expression profiles in Col-0 and agl9 agl15.CUT&Tag qPCR also demonstrated the occupancy of the two MADS-box proteins and FIS-PRC2 on a few representative target loci.Our studies suggest that MADS-box proteins could potentially recruit PRc2 to regulate many other developmental processes in plants or even in fungi and animals.