Expression of Pumpkin CmbHLH87 Gene Improves Powdery Mildew Resistance in Tobacco

Abstract

Powdery mildew (PM), caused by Podosphaera xanthii, is a major threat to the global cucurbit yield. The molecular mechanisms underlying the PM resistance of pumpkin (Cucurbita moschata Duch.) are largely unknown. A homolog of the basic helix-loop-helix (bHLH) transcription factor was previously identified through a transcriptomic analysis of a PM-resistant pumpkin. In this study, this bHLH homolog in pumpkin has been functionally characterized. CmbHLH87 is present in the nucleus. CmbHLH87 expression in the PMresistant material was considerably downregulated by PM; and abscisic acid, methyl jasmonate, ethephon, and NaCl treatments induced CmbHLH87 expression. Ectopic expression of CmbHLH87 in tobacco plants alleviated the PM symptoms on the leaves, accelerated cell necrosis, and enhanced H 2 O 2 accumulation. The expression levels of PR1a, PR5, and NPR1 were higher in the PM-infected transgenic plants than in PMinfected wild-type plants. Additionally, the chlorosis and yellowing of plant materials were less extensive and the concentration of bacteria at infection sites was lower in the transgenic tobacco plants than in the wild-type plants in response to bacterial wilt and scab pathogens. CmbHLH87 may be useful for genetic engineering of novel pumpkin cultivars in the future.

GWAS Reveals a Novel Candidate Gene CmoAP2/ERF in Pumpkin (Cucurbita moschata) Involved in Resistance to Powdery Mildew

“…In their study, Guo et al identified that six pumpkin genes, including bHLH87 (basic helix–loop–helix 87), ERF104 (ethylene response factor 104), WRKY21 , HSFA (heat shock factor A), MLO3 (mildew locus O), and SGT1 (suppressor of G2 allele of SKP1) were differentially regulated in PM-resistant line compared to the PM-sensitive line [ 4 ]. Moreover, the CmoSGT1 and CmobHLH87 genes were ectopically overexpressed in tobacco and found to enhance the PM resistance in the transgenic lines [ 64 , 65 ].…”

Genome-Wide Characterization and Analysis of the bHLH Transcription Factor Family in Suaeda aralocaspica, an Annual Halophyte With Single-Cell C4 Anatomy

“…In the present study, the majority of SabHLH genes were activated in dimorphic seeds and more transcripts were accumulated with the progression of brown seed germination ( Figure 5A ). According to Wang L. et al (2017) , during the germination process of dimorphic seeds of S. aralocaspica , the secondary metabolism (flavonoid and flavonol biosynthesis) pathway was activated earlier in brown seed compared with in black seed, with the seeds showing different germination behaviors in order to cope with the harsh and unpredictable environment ( Guo W. L. et al, 2020 ). In sheepgrass ( Leymus chinensis ), LcbHLH92 negatively regulates the accumulation of anthocyanins, with effects on seed coat color and reduction of seed dormancy ( Zhao et al, 2019 ).…”

Genome-Wide Identification of Powdery Mildew Responsive Long Non-Coding RNAs in Cucurbita pepo

“…), WRKY21, MLO3, and SGT1 were identified as candidate genes conferring PMresistance (Guo et al, 2018). Moreover, the overexpression of CmSGT1 (Guo et al, 2019) and CmbHLH87 (Guo et al, 2020) can increase PM resistance in tobacco. Although these studies increase our understanding of the mechanism of plant resistance to PM, the molecular mechanisms underlying the PM resistance in C. pepo remain largely unknown.…”