BoNR8 LncRNA And AtR8 LncRNA Were Involved In Hypocotyl Elongation Regulation By Light And ABA Signals

Hypocotyl is an embryonic part connecting cotyledons and roots,which is developed from cells located between apical meristems and basal meristems in mature embryos.The elongation of hypocotyl after seed germination is an important process of early photomorphogenesis of seedlings.Under dark conditions,Arabidopsis thaliana mainly inhibits photomorphogenesis and regulates hypocotyl elongation through the synergistic effect of COP/DET/ FUS complex and PIFs.Under light condition,the activated phytochrome is transferred from cytoplasm to nucleus to interact with PIFs and remove it,thus promoting the photomorphogenesis of Arabidopsis thaliana.Light significantly induced the expression of HY5 and increased its biological activity.HY5 promoted the photomorphogenesis of Arabidopsis seedlings by inhibiting the expression of genes related to hypocotyl elongation.Plant hormone abscisic acid(ABA)also inhibited hypocotyl elongation.At present,the molecular mechanism of hypocotyl elongation under the comprehensive regulation of light and ABA signals is still unclear.Long-chain noncoding RNA(lncRNA;>200nt)does not encode protein,which plays many physiological roles in organisms.BoNR8 lncRNA(272nt)is a long noncoding RNA transcribed by cabbage RNA polymerase III.AtR8 lncRNA(259nt)is a long noncoding RNA transcribed by Arabidopsis Polymerase III.Their sequence similarity is 77%,and the conserved sequence is mainly distributed in the stem of RNA secondary structure.Previous studies showed that BoNR8 lncRNA responded to salt and ABA stress and regulated seed germination and root growth of Arabidopsis thaliana,and AtR8 lncRNA participated in the innate immune function of Arabidopsis thaliana.In this study,it was found that the promoter regions of BoNR8 lncRNA and AtR8 lncRNA contain ABA signal response elements and light response elements.In-depth analysis shows that:1.dark condition significantly inhibited the expression of BoNR8 lncRNA,but the addition of 10μM ABA in the medium promoted the expression of BoNR8 lncRNA.Under normal conditions,the overexpression of BoNR8 lncRNA inhibited the elongation of hypocotyl,while the overexpression of BoNR8 lncRNA promoted the elongation of hypocotyl after ABA was added.Under dark conditions,the overexpression of BoNR8 lncRNA in Arabidopsis promoted the elongation of hypocotyl,and ABA addition also promoted the growth of hypocotyl.2.Dark conditions significantly promoted the expression of AtR8 lncRNA,and the addition of 10μM ABA in the medium inhibited the expression of AtR8 lncRNA.Under normal conditions,the overexpression of AtR8 lncRNA promoted the elongation of hypocotyl,while the overexpression of AtR8 lncRNA inhibited the elongation of hypocotyl after ABA was added.Under dark conditions,the overexpression of AtR8 lncRNA was the same as that of wild type,and the growth of the hypocotyl with AtR8 lncRNA overexpression was inhibited after ABA was added.3.Under light conditions,overexpression of BoNR8 inhibited the expressions of PHYB,HY5,COP1,ABI3 and ABI5.AtR8 overexpression inhibited the expression of PHYB,HY5 and COP1.Under dark conditions,overexpression of BoNR8 significantly inhibited the expressions of PHYB,HY5 and ABI3,and promoted the expressions of COP1,ABI5 and EM6.Overexpression of AtR8 significantly inhibited the expressions of PHYB,HY5 and PIF4,and promoted the expressions of COP1,ABI3,ABI5 and EM6.The overexpression of BoNR8 promoted the expression of PHYB,COP1,HY5,PIF4 and ABI5 under ABA irradiation.AtR8 overexpression promoted the expression of PHYB,COP1 and HY5.Overexpression of BoNR8 promoted the expressions of PHYB and PIF4 and inhibited the expressions of COP1,ABI3 and ABI5 under dark ABA treatment.AtR8 overexpression promoted the expressions of PHYB,PIF4,HY5 and ABI3,and inhibited the expressions of COP1,EM6 and ABI5.4.Biological information analysis shows that ABI3 gene promoter region has ABA response element ABRE and various light response sequence elements.The expression of ABI3 was significantly induced by dark conditions,and this induction was weakened after ABA was added.However,the expression of ABI3 gene was still significantly induced under relatively normal light culture conditions.Under dark with ABA condition,the hypocotyl of ABI3 deletion mutant was obviously elongated.The above results showed that BoNR8 lncRNA and AtR8 lncRNA regulated hypocotyl elongation in trans mainly by regulating the expression of light signal genes PHYB,COP1,HY5,PIF4 and ABI3.