Coexpression of PalbHLH1 and PalMYB90 Genes From Populus alba Enhances Pathogen Resistance in Poplar by Increasing the Flavonoid Content

Abstract

Secondary metabolites of the flavonoid pathway participate in plant defense, and bHLH and MYB transcription factors regulate the synthesis of these metabolites. Here, we define the regulatory mechanisms in response to pathogens. Two transcription factors from Populus alba var. pyramidalis, PalbHLH1 and PalMYB90, were overexpressed together in poplar, and transcriptome analysis revealed differences in response to pathogen infection. The transgenic plants showed elevated levels of several key flavonoid pathway components: total phenols, proanthocyanidins (PAs), and anthocyanins and intermediates quercetin and kaempferol. Furthermore, PalbHLH1 and PalMYB90 overexpression in poplar enhanced antioxidase activities and H 2 O 2 release and also increased resistance to Botrytis cinerea and Dothiorella gregaria infection. Gene expression profile analysis showed most genes involved in the flavonoid biosynthesis pathway or antioxidant response to be upregulated in MYB90/bHLH1-OE poplar, but significant differential expression occurred in response to pathogen infection. Specifically, expression of PalF3H (flavanone 3-hydroxylase), PalDFR (dihydroflavonol 4-seductase), PalANS (anthocyanin synthase), and PalANR (anthocyanin reductase), which function in initial, middle, and final steps of anthocyanin and PA biosynthesis, respectively, was significantly upregulated in D. gregaria-infected MYB90/ bHLH1-OE poplar. Our results highlight that PalbHLH1 and PalMYB90 function as transcriptional activators of flavonoid pathway secondary-metabolite synthesis genes, with differential mechanisms in response to bacterial or fungal infection.

PAL‐mediated SA biosynthesis pathway contributes to nematode resistance in wheat

“…Except for SA, numerous metabolite contents were decreased when AevPAL1 and AevTDC1 were silenced in the present study, including some metabolites known to be related to plant defense (Zhang et al ., 2017; Bai et al ., 2019; He et al ., 2020; Dong and Lin, 2020). It is noteworthy that some of these metabolites may be involved in resistance to nematodes.…”

Remote estimation of leaf area index (LAI) with unmanned aerial vehicle (UAV) imaging for different rice cultivars throughout the entire growing season

“…Noted that the Mini-MCA sensor sensitivity drops around 450 nm and the signal to noise ratio is relatively low at blue band [ 67 ]. On the other hand, rice reflectance at blue band is quite low due to vegetation high absorption of visible radiation [ 68 , 69 ], thus at blue band the quality of Mini-MCA images was not good. So in this study we avoided the VIs with blue reflectance.…”

“…So in this study we avoided the VIs with blue reflectance. EVI2 was used instead of EVI, since these two indices appeared very close in many studies [ 35 , 68 – 70 ].…”

Contribution of phenylpropanoid metabolism to plant development and plant–environment interactions

“…Glucosidases are responsible for the hydrolization of anthocyanin and flavonol to yield aglycones with more toxicity toward fungal pathogens (Sudheeran et al, 2020). Transcriptional upregulation of flavonoid structural genes such as F3H , FLS , DFR , ANS , and ANR , which function in initial, middle, and final steps of flavonol, anthocyanin, and proanthocyanidins biosynthesis, respectively, was found to promote the accumulation of quercetin, kaempferol, and anthocyanins and enhance resistance to Dothiorella gregaria infection in PalbHLH1 and PalMYB90 overexpression lines of Populus alba (Bai et al, 2020). Additionally, overexpression of F3H resulted in higher levels of flavonols such as kaempferol, isorhamnetin, and syringetin, reducing the oxidative damage and susceptibility to Colletotrichum sublineola , which is the causal agent of anthracnose in sorghum ( Sorghum bicolor ) (Wang et al, 2020b).…”