Dc GA20ox2 and DcGA2ox1 alter endogenous gibberellin contents and adjust lignin accumulation in carrot

Gibberellins(GAs)are a class of plant hormones that can affect plant growth and development.GA-oxidases are rate-limiting enzymes,which play a direct role in GA accumulation in plants.However,the roles of GA-oxidase on carrot(Daucus carota L.)taproot development are still unclear.In this study,two GA-oxidase genes,DcGA20ox2 and DcGA2ox1,were identified in carrot.Transgenic carrot plants were obtained by using Agrobacterium-mediated genetic transformation method.The results showed that overexpression of DcGA20ox2 significantly promoted the accumulation of active GAs in carrot,increased plant height,generated more branches,and enhanced xylem development.Overexpression of DcGA2ox1 significantly reduced the total contents of active GAs compared with the control group,resulting in a dwarf phenotype and markedly increased lignin content of the transgenic carrot.The expression profiling showed that the genes of GA metabolic pathway responded to the negative feedback regulation mechanism.At the same time,the expression of most genes in lignin biosynthesis and polymerization process was up-regulated,corresponding to the massive accumulation of lignin.These findings indicated that DcGA20ox2 and DcGA2ox1affected carrot growth and development by regulating the levels of endogenous GAs.The results from current work might shed light on further studies aimed to regulate lignification in carrot and other crops.

Synthesis of betanin by expression of the core betalain biosynthetic pathway in carrot

Betalain has received increased attention because of its high nutritional value and crucial physiological functions.Based on the elucidation of its core biosynthetic pathway,betalain can be produced in additional plants by metabolic engineering.Synthesis of betalain in carrot(Daucus carota L.)can improve its nutritional quality and economic value by extracting betalain from the fleshy root,non-edible part,and processing residue of carrot.In this study,two different constructs,namely,pYB:mCD(AomelOS,BvCYP76AD1S,and BvDODA1S)and p YB:CDD(BvCYP76AD1S,BvDODA1S,and MjcDOPA5GTS),were introduced into carrot for betanin synthesis by Agrobacterium-mediated transformation.Betanin can be synthetized in both transgenic calli,and p YB:m CD-transgenic callus can be used to produce betacyanin by suspension culture.However,pYB:mCD-transgenic seedlings can synthetize betanin only by tyrosine feeding.The p YB:CDD-transgenic lines can synthetize betanin in whole plants.The betanin content in fleshy root of pYB:CDD-transgenic carrot was(63.4±9)μg·g^(-1)fresh weight according to quantitative analysis.These betanin-producing carrot plant materials can be used to synthesize betanin for industrial application or consumption as dietary sources.

Transcriptomic analysis of interstockinduced dwarfism in Sweet Persimmon(Diospyros kaki Thunb.)

Growth monitoring indicated that the height of‘Kanshu’plants with‘Nantong-xiaofangshi’as an interstock was significantly shorter than that of‘Kanshu’plants with no interstock.A transcriptome analysis of the two graft combinations(‘Kanshu’/Diospyros lotus and‘Kanshu’/‘Nantong-xiaofangshi’/Diospyros lotus)was conducted to explore the dwarfing genes related to the use of the‘Nantong-xiaofangshi’interstock.Hormone levels and water conductance were also measured in these two graft combinations.The results indicated that the levels of both IAA and GA were lower in‘Kanshu’that had been grafted onto the‘Nantong-xiaofangshi’interstock than in‘Kanshu’with no interstock;additionally,the water conductance was lower in grafts with interstocks than in grafts without interstocks.The expression of AUX/IAA and auxin-responsive GH3 genes was enhanced in scions grafted on the interstock and was negatively correlated with the IAA content and growth of scions.The expression of GA2ox,DELLA,and SPINDLY genes were also upregulated and associated with a decrease in the level of GA in scions grafted on the interstock.Since one of the GA2ox unigenes was annotated as DkGA2ox1 in Diospyros kaki,but was not functionally validated,a functional analysis was conducted in transgenic tobacco.Overexpression of DkGA2ox1 in transgenic plants resulted in a dwarf phenotype that could be recovered by the exogenous application of GA3.We conclude that the‘Nantong-xiaofangshi’interstock affects the water conductance and expression of genes related to the metabolism and transduction of IAA and GA in the grafted scion and thus regulates phytohormone levels,producing dwarfing.

A betaxanthin-based visible and fluorescent reporter for monitoring plant transformation

Commonly used reporters rely on a single property,such as the fluorescence of GFP and visible color of anthocyanins,therefore these reporters hardly handle the complicated condition in practice.Betaxanthins are a group of plant natural products derived from the amino acid tyrosine.Its visible yellow-orange color and green fluorescence under blue light make it a promising new reporter.Only two enzymatic reactions are required to convert tyrosine into betaxanthins.Here,we synthesized an open reading frame named Bx that contained all the betaxanthins biosynthetic genes and demonstrated its use as a powerful and efficient reporter in tobacco,carrot,and tomato.