Katchen Julliany P. Silva, Asha M. Brunings, Juliana A. Pereira, Natalia A. Peres, Kevin M. Folta and Zhonglin Mou

BMC Plant BiologyBMC Published: 1 December 2017, 17:230

Abstract

Background

Plant immune response is associated with a large-scale transcriptional reprogramming, which is regulated by numerous transcription regulators such as the Elongator complex. Elongator is a multitasking protein complex involved in diverse cellular processes, including histone modification, DNA methylation, and tRNA modification. In recent years, Elongator is emerging as a key regulator of plant immune responses. However, characterization of Elongator’s function in plant immunity has been conducted only in the model plant Arabidopsis thaliana. It is thus unclear whether Elongator’s role in plant immunity is conserved in higher plants. The objective of this study is to characterize transgenic woodland strawberry (Fragaria vesca L.) overexpressing the Arabidopsis Elongator (AtELP) genes, AtELP3 and AtELP4, and to determine whether F. vesca carries a functional Elongator complex.

Methods

Transgenic F. vesca and Arabidopsis plants were produced via Agrobacterium-mediated genetic transformation and characterized by morphology, PCR, real-time quantitative PCR, and disease resistance test. The Student’s t test was used to analyze the data.

Results

Overexpression of AtELP3 and AtELP4 in F. vesca impacts plant growth and development and confers enhanced resistance to anthracnose crown rot, powdery mildew, and angular leaf spot, which are caused by the hemibiotrophic fungal pathogen Colletotrichum gloeosporioides, the obligate biotrophic fungal pathogen Podosphaera aphanis, and the hemibiotrophic bacterial pathogen Xanthomonas fragariae, respectively. Moreover, the F. vesca genome encodes all six Elongator subunits by single-copy genes with the exception of FvELP4, which is encoded by two homologous genes, FvELP4–1 and FvELP4–2. We show that FvELP4–1 complemented the Arabidopsis Atelp4/elo1–1 mutant, indicating that FvELP4 is biologically functional.

Conclusions

This is the first report on overexpression of Elongator genes in plants. Our results indicate that the function of Elongator in plant immunity is most likely conserved in F. vesca and suggest that Elongator genes may hold potential for helping mitigate disease severity and reduce the use of fungicides in strawberry industry.

See: https://bmcplantbiol.biomedcentral.com/articles/10.1186/s12870-017-1173-5

Figure 1: Molecular and morphological characterization of transgenic F. vesca plants expressing AtELP3 and AtELP4. a and b Expression levels of AtELP3 (a) and AtELP4 (b) in independent AtELP3 (E3) and AtELP4 (E4) transgenic F. vesca lines. No AtELP3 and AtEL4 expression was detected in the non-transformed control (Cont.). The order of the transgenic lines is presented in order of increasing expression levels of the transgene. Expression of the transgene was normalized against the constitutively expressed EF1α gene. The resulting average values of E3/69 and E4/51 were arbitrarily set as 1 in (a) and (b), respectively, and other lines were compared with E3/69 or E4/51 to show the relative expression levels of the transgenes. Data represent the average of three biological replicates with standard deviation (SD). The experiments were repeated with similar trends. c Presence (+) or absence (−) of runners, flowers, and fruit on the AtELP3 (E3) and AtELP4 (E4) transgenic plants. The order of the transgenic lines is the same as in Fig. 1a and b. d Plant (top) and fruit (bottom) morphology of two AtELP3 (E3/66 and E3/72) and two AtELP4 (E4/06 and E4/01) transgenic lines as well as the non-transformed control (Cont.). e and f Plant height (e) and fruit weight (f) of one-year-old AtELP3 (E3) and AtELP4 (E4) transgenic plants. The fruit weight data in (f) represent the average of 20 strawberries with SD. An asterisk indicates significant difference between the transgenic line and the non-transformed control (Cont.) (Student’s t-test, p < 0.05).