Genome-Wide Analysis of Specific PfR2R3-MYB Genes Related to Paulownia Witches' Broom

Overexpression of a 'Paulownia fortunei' MYB Factor Gene, PfMYB44, Increases Salt and Drought Tolerance in Arabidopsis thaliana

Paulownia fortunei (Seem.) Hemsl is a Paulownia Sieb.et tree of the family Scrophulariaceae. It has become an important short-to-medium-term fast-growing multi-purpose tree species in China due to its rapid growth, strong adaptability, and excellent material properties. MYB transcription factors in plants have numerous and diverse functions, playing important roles in various aspects such as plant stress response. To investigate the function of MYB transcription factors in Paulownia fortunei, this study used PCR technology to clone the PfMYB44 gene from Paulownia fortunei. The homology of PfMYB44 and SiMYB44 (Sesamum indicum) was the highest. Expression analysis results showed that PfMYB44 was expressed in the root, stem, young leaf, and mature leaf of Paulownia fortunei, with the highest content in the root. Cold, drought, hot, salt, and ABA treatments could increase the expression level of PfMYB44. Overexpression-PfMYB44 plants were constructed, and physiological and molecular analysis showed that PfMYB44 could positively regulate salt and drought stresses. Under drought stress, the expression levels of AtP5CS, AtCAT1, AtNCED3 and AtSnRK2.4 in transgenic lines were significantly induced. Salt stress induced the expression of AtNHX1, AtSOS1, AtSOS2 and AtSOS3 genes, and the relative expression levels of these genes in transgenic Arabidopsis were higher. In conclusion, the functional study of PfMYB44 laid a certain foundation for the study of Paulownia stress resistance, and was helpful to the study of its stress resistance mechanism and the cultivation of new stress resistance varieties.

Identification and Analysis of PPO Gene Family Members in Paulownia fortunei

Polyphenol oxidase (PPO) is a common metalloproteinase in plants with important roles in plant responses to abiotic and biotic stresses. There is evidence that PPOs contribute to stress responses in Paulownia fortunei. In this study, PPO gene family members in P. fortunei were comprehensively identified and characterized using bioinformatics methods as well as analyses of phylogenetic relationships, gene and protein structure, codon usage bias, and gene expression in response to stress. The genome contained 10 PPO gene family members encoding 406-593 amino acids, with a G/C bias. Most were localized in chloroplasts. The motif structure was conserved among family members, and α-helices and random coils were the dominant elements in the secondary structure. The promoters contained many cis-acting elements, such as auxin, gibberellin, salicylic acid, abscisic acid, and photoresponsive elements. The formation of genes in this family was linked to evolutionary events, such as fragment replication. Real-time quantitative PCR results showed that PfPPO7, PfPPO10, PfPPO1, PfPPO2, PfPPO3, PfPPO4, PfPPO5, and PfPPO8 may be key genes in drought stress resistance. PfPPO1, PfPPO3, PfPPO4, and PfPPO10 were resistant stress-sensitive genes. These results provide a reliable basis for fully understanding the potential functions of these genes and the selection of resistance breeding.

Bioinformatic Analysis of the BTB Gene Family in Paulownia fortunei and Functional Characterization in Response to Abiotic and Biotic Stresses

To learn about the gene structure, phylogenetic evolution, and function under biotic and abiotic stresses of BTB (Bric-a-Brac/Tramtrack/Broad Complex) genes in Paulownia fortunei, a whole-genome sequence evaluation was carried out, and a total of 62 PfBTB genes were identified. The phylogenetic analysis showed that PfBTB proteins are divided into eight groups, and these proteins are highly conserved. PfBTB genes were unevenly distributed on 17 chromosomes. The colinearity analysis found that fragment replication and tandem replication are the main modes of gene amplification in the PfBTB family. The analysis of cis-acting elements suggests that PfBTB genes may be involved in a variety of biological processes. The transcriptomic analysis results showed that PfBTB3/12/14/16/19/36/44 responded to Paulownia witches' broom (PaWB), while PfBTB1/4/17/43 responded to drought stress, and the RT-qPCR results further support the reliability of transcriptome data. In addition, the association analysis between miRNA and transcriptome revealed a 91-pair targeting relationship between miRNAs and PfBTBs. In conclusion, the BTB genes in Paulownia are systematically identified in this research. This work provides useful knowledge to more fully appreciate the potential functions of these genes and their possible roles in the occurrence of PaWB and in response to stress.