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Hydroxycinnamoyl-CoA quinate hydroxycinnamoyl transferase (HQT) is the key enzyme in the biosynthetic pathway of chlorogenic acid. A homologous gene of NtHQT from Nicotiana tabacum was cloned and named NtHQT2. Amino acid sequence alignment and phylogenetic analysis revealed that NtHQT2 possessed the conserved HTLSD and DEFEG motifs of HQT protein and belonged to the same branch with HQTs from tobacco and other Solanaceae plants in terms of evolutionary relationships. By analyzing the expression patterns of NtHQT2 gene in different tissues of tobacco by qRT-PCR analysis, it was found that NtHQT2 gene was expressed in the root, stalk, leaf, axillary bud, and flower with higher expression levels observed in the leaves. CRISPR/Cas9 gene editing technology was used to perform targeted knockout of NtHQT2 gene, and three types of T0 generation gene-edited plants with NtHQT2 translation error were obtained. By quantifying the chlorogenic acid content in the leaves of homozygous T2 NtHQT2 gene-edited plants, it was observed that the edited plants exhibited a significant decrease in chlorogenic acid content compared to the control, indicating that NtHQT2 gene positively regulates the synthesis of chlorogenic acid. [ABSTRACT FROM AUTHOR]

Many pathovars of plant pathogenic bacteria Xanthomonas species inject transcription activator-like (TAL) effectors into plant host cells to promote disease susceptibility or trigger disease resistance. The rice TAL effector-dependent disease resistance gene Xa10 confers narrow-spectrum race-specific resistance to Xanthomonas oryzae pv. oryzae ( Xoo), the causal agent of bacterial blight disease in rice. To generate broad-spectrum and durable resistance to Xoo, we developed a modified Xa10 gene, designated as Xa10 E5. Xa10 E5 has an EBE-amended promoter containing 5 tandemly arranged EBEs each responding specifically to a corresponding virulent or avirulent TAL effector and a stable transgenic rice line containing Xa10 E5 was generated in the cultivar Nipponbare. The Xa10 E5 gene was specifically induced by Xoo strains that harbour the corresponding TAL effectors and conferred TAL effector-dependent resistance to the pathogens at all developmental stages of rice. Further disease evaluation demonstrated that the Xa10 E5 gene in either Nipponbare or 9311 genetic backgrounds provided broad-spectrum disease resistance to 27 of the 28 Xoo strains collected from 11 countries. The development of Xa10 E5 and transgenic rice lines provides new genetic materials for molecular breeding of rice for broad-spectrum and durable disease resistance to bacterial blight. [ABSTRACT FROM AUTHOR]

The recognition between disease resistance (R) genes in plants and their cognate avirulence (Avr) genes in pathogens can produce a hypersensitive response of localized programmed cell death. However, our knowledge of the early signaling events of the R gene–mediated hypersensitive response in plants remains limited. Here, we report the cloning and characterization of Xa10 , a transcription activator–like (TAL) effector-dependent R gene for resistance to bacterial blight in rice (Oryza sativa). Xa10 contains a binding element for the TAL effector AvrXa10 (EBE  AvrXa10) in its promoter, and AvrXa10 specifically induces Xa10 expression. Expression of Xa10 induces programmed cell death in rice, Nicotiana benthamiana , and mammalian HeLa cells. The Xa10 gene product XA10 localizes as hexamers in the endoplasmic reticulum (ER) and is associated with ER Ca2+ depletion in plant and HeLa cells. XA10 variants that abolish programmed cell death and ER Ca2+ depletion in N. benthamiana and HeLa cells also abolish disease resistance in rice. We propose that XA10 is an inducible, intrinsic terminator protein that triggers programmed cell death by a conserved mechanism involving disruption of the ER and cellular Ca2+ homeostasis. [ABSTRACT FROM AUTHOR]

Cinnamyl alcohol dehydrogenase (CAD) plays a crucial role in lignin biosynthesis, and the gene family encoding various CAD isozymes has been cloned and characterized in numerous plant species. However, limited information regarding the CAD gene family in tobacco is currently available. In this study, we identified 10 CAD genes in Nicotiana tabacum , four in N. tomentosiformis , and six in N. sylvestris . The nucleotide and amino acid sequences of these tobacco CADs demonstrate high levels of similarity, whereas the putative protein sequences conservatively possessed two Zn 2+ binding motifs and an NADP(H) cofactor binding motif. Both NtCAD1 and NtCAD2 had conservative substrate binding sites, similar to those possessed by bona fide CADs, and evidence from phylogenetic analysis as well as expression profiling supported their role as bona fide CADs involved in lignin biosynthesis. NtCAD1 has two paralogous genes, NtCAD1-1 and NtCAD1-2 . Enzyme activity analysis revealed that NtCAD1-1 and NtCAD1-2 had a high affinity to coniferyl aldehyde, p -coumaryl aldehyde, and sinapyl aldehyde, whereas NtCAD2 preferred coniferyl aldehyde and p -coumaryl aldehyde as substrates. The kinetic parameter assay revealed that NtCAD1-2 functions as the most efficient enzyme. Downregulation of both NtCAD1-1 and NtCAD1-2 resulted in reddish-brown stems without significant changes in lignin content. Furthermore, NtCAD1-1, NtCAD1-2, and NtCAD2 showed distinct expression patterns in response to biotic and abiotic stresses, as well as different phytohormones. Our findings suggest that NtCAD1-1 and NtCAD1-2 are involved in lignin biosynthesis, with NtCAD1-2 also participating in both biological and abiotic stresses, whereas NtCAD2 plays a distinct role mainly in responding to biological and abiotic stresses in tobacco., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Wu, Li, Liu, Xia, Xiang, Zhao, Yang, Li, Xie, Wang, Wang, Xu and Yang.)