Identification, isolation, and expression analysis of heat shock transcription factors in the diploid woodland strawberry Fragaria vesca

Abstract

Heat shock transcription factors (Hsfs) are known to play dominant roles in plant responses to heat, as well as other abiotic or biotic stress stimuli. While the strawberry is an economically important fruit plant, little is known about the Hsf family in the strawberry. To explore the functions of strawberry Hsfs in abiotic and biotic stress responses, this study identified 17 Hsf genes (FvHsfs) in a wild diploid woodland strawberry (Fragaria vesca, 2n = 2x = 14) and isolated 14 of these genes. Phylogenetic analysis divided the strawberry FvHsfs genes into three main groups. The evolutionary and structural analyses revealed that the FvHsf family is conserved. The promoter sequences of the FvHsf genes contain upstream regulatory elements corresponding to different stress stimuli. In addition, 14 FvHsf-GFP fusion proteins showed differential subcellular localization in Arabidopsis mesophyll protoplasts. Furthermore, we examined the expression of the 17 FvHsf genes in wild diploid woodland strawberries under various conditions, including abiotic stresses (heat, cold, drought, and salt), biotic stress (powdery mildew infection), and hormone treatments (abscisic acid, ethephon, methyl jasmonate, and salicylic acid). Fifteen of the seventeen FvHsf genes exhibited distinct changes on the transcriptional level during heat treatment. Of these 15 FvHsfs, 8 FvHsfs also exhibited distinct responses to other stimuli on the transcriptional level, indicating versatile roles in the response to abiotic and biotic stresses. Taken together, the present work may provide the basis for further studies to dissect FvHsf function in response to stress stimuli.

Identification of Heat Shock Transcription Factor Genes Involved in Thermotolerance of Octoploid Cultivated Strawberry

“…These data revealed that FaTHSFA2a and FaTHSFB1a proteins were not confined in the nucleus; they can be transferred into the cytoplasm where they might conceivably perform other functions. Our results are in concordance with previous data reported by Hu et al (2015) [53]; they clearly detected most FvHSF–GFP proteins in the nucleus. However, some FvHSF–GFP proteins, including FvHSF2a, FvHSF3a, FvHSF4a, FvHSF5a, FvHSF2b, and FvHSFC1a, remained detectable in the cytosol [53].…”

“…Our results are in concordance with previous data reported by Hu et al (2015) [53]; they clearly detected most FvHSF–GFP proteins in the nucleus. However, some FvHSF–GFP proteins, including FvHSF2a, FvHSF3a, FvHSF4a, FvHSF5a, FvHSF2b, and FvHSFC1a, remained detectable in the cytosol [53]. Thus, our results revealed that FaTHSFA2a and FaTHSFB1a proteins have the capability to enter the nucleus and putatively function as transcriptional regulators.…”

“…Among the wild-type diploid woodland strawberry F. vesca , which was composed of 17 classified FvHSF genes, namely 11 class A, five class B, and one class C genes, only 14 genes were isolated, including FvHSFA4b and FvHSFA7a (class A). Hu et al (2015) could not isolate FvHSFA8a from class A HSFs [53]. In our study, other class A subgroup (A3, A7, and A9), class B subgroup (B2), and class C HSF genes could not be identified either because our collected tissues were not subjected to heat stress before transcriptome analysis, resulting in lower expression of those genes, or complete lack of those genes in F. × ananassa Duch.…”

“…In addition, further overexpression of FaTHSFA2a and FaTHSFB1a in transgenic Arabidopsis enhanced plant resistance to heat stress, indicating that these genes play crucial roles in plants’ thermotolerance by using “gain of function” strategies. Thus, this is the major difference between our studies and those reported by Hu et al [53]. We mainly focused on functional assays, whereas they intended to discover whether all the HSF-related genes exhibited differential changes at the transcriptional level following heat treatment.…”

Heat shock transcription factors in banana: genome-wide characterization and expression profile analysis during development and stress response

“…After initially identified in yeast6, plant Hsf gene family has been identified and characterized in more and more plant species, including alfalfa ( Medicago sativa L.)21, Arabidopsis thaliana 22, rice ( Oryza sativa L.)2324, maize ( Zea mays L.)25, Medicago truncatula, Populus trichocarpa 26, wheat ( Triticum aestivum L.)27, soybean ( Glycine max )2829, Chinese cabbage ( Brassica rapa ssp. pekinensis )1030, cotton ( Gossypium hirsutum )31, pigeonpea ( Cajanus cajan ), barrel medic ( Medicago truncatula )32, pepper ( Capsicum annuum L.)3334, pear ( Pyrus bretschneideri )35, Populus euphratica 36, strawberry ( Fragaria vesca )37, tea plant ( Camellia sinensis )38, wild Chinese grapevine ( Vitis pseudoreticulata )39, etc.…”