Plants are sessile organisms that have acquired highly plastic developmental strategies to adapt to the environment.Among these processes,the floral transition is essential to ensure reproductive success and is finelyregulated by several internal andexternal genetic networks.The photoperiodic pathway,which controls plant response to day length,is one of the most important pathways controlling flowering.In Arabidopsis photoperiodic flowering,CONSTANS(CO)is the central gene activating the expression of the florigen FLOWERING LOCUS T(FT)in the leaves at the end of a long day.The circadian clock strongly regulates Co expression.However,to date,no evidence has been reported regarding a feedbackloop from the photoperiod pathway back to the circadian clock.Using transcriptional networks,we have identified relevant network motifs regulating the interplay between the circadian clock and the photoperiod pathway.Gene expression,chromatin immunoprecipitation experiments,and phenotypic analysis allowed us to elucidate the role of Co over the circadian clock.Plants with altered cO expression showed a different internal clock period,measured by daily leaf rhythmic movements.We showed that co upregulates the expression of key genes related to the circadian clock,such as CCA1,LHY,PRR5,and Gl,at the end of a long day by bindingto specific sites on their promoters.Moreover,a high numberof PRR5-repressed target genes are upregulated by CO,and this could explain the phase transition promoted by CO.The CO-PRR5 complex interacts with the bZiP transcriptionfactor HY5andhelps to localize the complex in the promoters of clock genes.Taken together,our results indicate that there may be a feedback loop in which co communicates back to the circadian clock,providing seasonal information to the circadian system.
Pedro de los ReyesGloria Serrano-BuenoFrancisco J.Romero-CamperoHe GaoJose M.RomeroFederico Valverde
Human beings live in a world defined by daily cycles of light and darkness caused by the Earth’s rotation around its axis.Plants,like most living organisms,have evolved internal circadian clocks that time biological processes in anticipation of these daily environmental changes(Young and Kay,2001).The plant clock relies on core genes encoding transcription factors(TFs),which regulate each other’s expression through intricate networks of interlocking transcriptional-translational feedback loops(Nohales and Kay,2016).These loops ultimately control the expression of thousands of genes,allowing plants to adapt to daily fluctuations in light,temperature,and humidity(Covington et al.,2008).In addition to daily rhythms,the Earth experiences yearly seasonal cycles marked by longer,warmer days in spring and summer,followed by shorter,cooler days in autumn and winter.Seasonal changes in day length and temperature intensify with distance from the equator.Consequently,the ability of plants to adjust their growth and development in anticipation of seasonal changes determines their latitudinal distribution(McMillan,1960).
Pyrus pyrifolia Nakai‘Whangkeumbae'is a sand pear fruit with excellent nutritional quality and taste.However,the industrial development of pear fruit is significantly limited by its short shelf life.Salicylic acid(SA),a well-known phytohormone,can delay fruit senescence and improve shelf life.However,the mechanism by which SA regulates CONSTANS-LIKE genes(COLs)during fruit senescence and the role of COL genes in mediating fruit senescence in sand pear are poorly understood.In this study,22 COL genes were identified in sand pear,including four COLs(Pp COL8,Pp COL9a,Pp COL9b,and Pp COL14)identified via transcriptome analysis and 18 COLs through genome-wide analysis.These COL genes were divided into three subgroups according to the structural domains of the COL protein.Pp COL8,with two B-box motifs and one CCT domain,belonged to the first subgroup.In contrast,the other three Pp COLs,Pp COL9a,Pp COL9b,and Pp COL14,with similar conserved protein domains and gene structures,were assigned to the third subgroup.The four COLs showed different expression patterns in pear tissues and were preferentially expressed at the early stage of fruit development.Moreover,the expression of Pp COL8 was inhibited by exogenous SA treatment,while SA up-regulated the expression of Pp COL9a and Pp COL9b.Interestingly,Pp COL8 interacts with Pp MADS,a MADS-box protein preferentially expressed in fruit,and SA up-regulated its expression.While the production of ethylene and the content of malondialdehyde(MDA)were increased in Pp COL8-overexpression sand pear fruit,the antioxidant enzyme(POD and SOD)activity and the expression of Pp POD1 and Pp SOD1 in the sand pear fruits were down-regulated,which showed that Pp COL8 promoted sand pear fruit senescence.In contrast,the corresponding changes were the opposite in Pp MADS-overexpression sand pear fruits,suggesting that Pp MADS delayed sand pear fruit senescence.The co-transformation of Pp COL8 and Pp MADS also delayed sand pear fruit senescence.The results of this study revealed that Pp COL8 can
Stigma color is a critical agronomic trait in watermelon that plays an important role in pollination.However,there are few reports on the regulation of stigma color in watermelon.In this study,a genetic analysis of the F2 population derived from ZXG1553(P1,with orange stigma)and W1-17(P2,with yellow stigma)indicated that stigma color is a quantitative trait and the orange stigma is recessive compared with the yellow stigma.Bulk segregant analysis sequencing(BSA-seq)revealed a 3.75 Mb segment on chromosome 6 that is related to stigma color.Also,a major stable effective QTL Clqsc6.1(QTL stigma color)was detected in two years between cleaved amplified polymorphic sequencing(CAPS)markers Chr06_8338913 and Chr06_9344593 spanning a~1.01 Mb interval that harbors 51 annotated genes.Cla97C06G117020(annotated as zinc finger protein CONSTANS-LIKE 4)was identified as the best candidate gene for the stigma color trait through RNA-seq,quantitative real-time PCR(qRT-PCR),and gene structure alignment analysis among the natural watermelon panel.The expression level of Cla97C06G117020 in the orange stigma accession was lower than in the yellow stigma accessions with a significant difference.A nonsynonymous SNP site of the Cla97C06G117020 coding region that causes amino acid variation was related to the stigma color variation among nine watermelon accessions according to their re-sequencing data.Stigma color formation is often related to carotenoids,and we also found that the expression trend of ClCHYB(annotated asβ-carotene hydroxylase)in the carotenoid metabolic pathway was consistent with Cla97C06G117020,and it was expressed in low amounts in the orange stigma accession.These data indicated that Cla97C06G117020 and ClCHYB may interact to form the stigma color.This study provides a theoretical basis for gene fine mapping and mechanisms for the regulation of stigma color in watermelon.
Shuang PeiZexu WuZiqiao JiZheng LiuZicheng ZhuFeishi LuanShi Liu