Inheritance and allelism of morphological traits in eastern redbud (Cercis canadensis L.)

Inheritance of purple,gold,and variegated foliage types,weeping architecture,and double flower was explored in F1,F2,and backcross families resulting from controlled hybridization of eastern redbud(Cercis canadensis L.).Potential allelic relationships were explored when possible.Inheritance analysis in families derived from controlled hybridization of‘Covey’(green leaf)and‘Forest Pansy’(purple leaf)suggest that purple leaf color and weeping architecture are both controlled by single recessive genes,for which the symbols pl1 and wp1 are proposed,respectively.Inheritance of gold leaf was explored in families of‘Covey’(green leaf)בHearts of Gold’(gold leaf).Interpretation of inheritance of gold leaf in these families was confounded by the recovery of a leaf color phenotype in the F2 family unlike either parent.However,data suggested the action of a single locus controlling gold leaf color in‘Hearts of Gold’,and that instability of gold leaf expression may be based on transposable element activity.Segregation of gold leaf in the F2 families of‘Texas White’[green leaf(C.canadensis var.texensis)]בJN2’[gold leaf(The Rising Sun)]did not fit a Mendelian ratio.Analysis of progeny of‘Silver Cloud’and‘Floating Clouds’(both showing white/green leaf variegation)with non-variegated cultivars demonstrated that variegation in‘Silver Cloud’is controlled by a single recessive nuclear gene,while variegation in‘Floating Clouds’is controlled by cytoplasmic factors.The symbol var1 is proposed for the gene controlling variegation in‘Silver Cloud’.Double flower in progeny derived from‘Flame’(double flower)suggested that double flower is dominant to single flower,and that‘Flame’is heterozygous at the double-flower locus,for which the symbol Df1 is proposed.Allelism studies showed that the gene controlling purple leaf in‘Forest Pansy’is allelic to the purple leaf gene in‘Greswan’and that the gene controlling weeping phenotype in‘Traveller’(C.canadensis var.texensis)is non-allelic to the weeping gene found in‘Covey’.Allelism of the gold leaf trait in‘Hearts of Gold’and‘JN2’was investigated,but no clear conclusions regarding allelism could be made due to recovery of leaf color phenotypes unlike either parent.

Evolution and roles of cytokinin genes in angiosperms 2:Do ancient CKXs play housekeeping roles while non-ancient CKXs play regulatory roles?

Cytokinin oxidase/dehydrogenase(CKX)is a key enzyme responsible for the degradation of endogenous cytokinins.However,the origins and roles of CKX genes in angiosperm evolution remain unclear.Based on comprehensive bioinformatic and transgenic plant analyses,we demonstrate that the CKXs of land plants most likely originated from an ancient chlamydial endosymbiont during primary endosymbiosis.We refer to the CKXs retaining evolutionarily ancient characteristics as“ancient CKXs”and those that have expanded and functionally diverged in angiosperms as“non-ancient CKXs”.We show that the expression of some non-ancient CKXs is rapidly inducible within 15 min upon the dehydration of Arabidopsis,while the ancient CKX(AtCKX7)is not drought responsive.Tobacco plants overexpressing a non-ancient CKX display improved oxidative and drought tolerance and root growth.Previous mutant studies have shown that non-ancient CKXs regulate organ development,particularly that of flowers.Furthermore,ancient CKXs preferentially degrade cis-zeatin(cZ)-type cytokinins,while non-ancient CKXs preferentially target N6-(Δ2-isopentenyl)adenines(iPs)and trans-zeatins(tZs).Based on the results of this work,an accompanying study(Wang et al.https://doi.org/10.1038/s41438-019-0211-x)and previous studies,we hypothesize that non-ancient CKXs and their preferred substrates of iP/tZ-type cytokinins regulate angiosperm organ development and environmental stress responses,while ancient CKXs and their preferred substrates of cZs play a housekeeping role,which echoes the conclusions and hypothesis described in the accompanying report(Wang,X.et al.Evolution and roles of cytokinin genes in angiosperms 1:Doancient IPTs play housekeeping while non-ancient IPTs play regulatory roles?Hortic Res 7,(2020).https://doi.org/10.1038/s41438-019-0211-x).