Abstract
Flavonoids are key secondary metabolites that are biologically active and perform diverse functions in plants such as stress defense against abiotic and biotic stress. In addition to its importance, no comprehensive information has been available about the secondary metabolic response of Populus tree, especially the genes that encode key enzymes involved in flavonoid biosynthesis under drought stress. In this study, the quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that the expression of flavonoid biosynthesis genes (PtPAL, Pt4-CL, PtCHS, PtFLS-1, PtF3H, PtDFR, and PtANS) gradually increased in the leaves of hybrid poplar (P. tremula × P. alba), corresponding to the drought stress duration. In addition, the activity and capacity of antioxidants have also increased, which is positively correlated with the increment of phenolic, flavonoid, anthocyanin, and carotenoid compounds under drought stress. As the drought stress prolonged, the level of reactive oxygen species such as hydrogen peroxide (H2O2) and singlet oxygen (O2−) too increased. The concentration of phytohormone salicylic acid (SA) also increased significantly in the stressed poplar leaves. Our research concluded that drought stress significantly induced the expression of flavonoid biosynthesis genes in hybrid poplar plants and enhanced the accumulation of phenolic and flavonoid compounds with resilient antioxidant activity.
Highlights
The plant growth and survival are greatly affected by water availability and different environmental constraints [1]
Under drought stress, the expression levels of DFR and anthocyanins synthase (ANS) were much higher. Both genes in the D15 plants were three to four times higher than those in the D0 plants (Figure 4F,G). All these results indicate that the application of drought stress significantly increased the expression of flavonoid biosynthesis genes
Based on the results of our study, we have concluded that antioxidants including flavonoids are very important secondary metabolites for Populus plants to cope with harsh environmental conditions
Summary
The plant growth and survival are greatly affected by water availability and different environmental constraints [1]. Plants adapt various strategies to cope with drought stress and oxidative damage, including maximizing the use of water, minimizing loss of water [9,10], developing antioxidant systems [11,12], and various biochemical, morphological, and physiological drought-resistance mechanisms to compensate for water lose [13,14]. Drought resistance is a complicated trait that is regularized by different genes, associations between genes and environmental signals, involving. Drought resistance is a complicated trait that is regularized by different genes, associations between genes and environmental signals, minvanoylvmingormphaonlyogmicoarlpahnodlomgiecatalbaonldicmpaetahbwoaliycsp[a1t5h].wTahyse [g1e5n]e. Athlrteheoucagrhbothnesi.rAfultnhcotuiognhstahnedir sfturnucc-ttuiorness aanreddsitvruercstue,reflsaavroendoiivdesrasere, fulasvuoanlloyiddserairveeudstuharlolyugdhertihveedphthernoyulgphrotphaenpehpeantyhlwpraoy(psaencoenpdaatrhywmayet(asbeocolincdpaartyhwmaeyta).bIonlitchpisapthawthawy)a.yI,nthtehicshpaalctohnweasyy,nththeacsheailsctohneeesnytnrythpaoseinits, cthaetaleynztirnyg pthoeincto,ncvaetrasliyozninogf mthaeloncoynl-vCeorAsioanndo4f -cmoaulmonayrol-yCCoAoAatnodch4a-lccoounme,atrhoeyreCbyoAinittioachtianlgcothnee,btihoesyrenbthyeisnisitoiaftflinagvothneoibdiso[s2y1n].thTehseismoafjoflraevnoznyomidess [e2n1t]a.nTghleedminajtohre efonrzmymateiosneonfvtaanrigolueds flianvtohneoifdosrminactluiodne ochf avlcaorinoeuissofmlaevroansoei(dCsHiIn)c, lfluadveancohnaelc3o-nheydisroomxyelraassee(F(3CHH)I,)d, ifhlay-dvaronfloanveon3o-hl y4d-rreodxuycltaassee ((DF3FHR)),, fldaivhoyndorlosflyanvtohnaosel (4F-SrHed)u, actnadseev(eDnFtuRa)l,lyfltahveoannotlhoscyynathnainsse s(FySnHth)a, saen(dAeNvSen) t(uFiaglluyreth1e).anthocyanins synthase (ANS) (Figure 1)
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