Phenotypic Characteristics and Transcriptome of Cucumber Male Flower Development Under Heat Stress

Abstract

Cucumber (Cucumis sativus L.) is an important vegetable crop, which is thermophilic not heat resistant. High-temperature stress always results in sterility at reproductive stage. In the present study, we evaluate the male flower developmental changes under normal (CK) and heat stress (HS) condition. After HS, the activities of peroxidase (POD) and superoxide dismutase (SOD) and the contents of malondialdehyde (MDA) were increased. In addition, the pollen fertility was significantly decreased; and abnormal tapetum and microspore were observed by paraffin section. Transcriptome analysis results presented that total of 5828 differentially expressed genes (DEGs) were identified after HS. Among these DEGs, 20 DEGs were found at four stages, including DNA binding transcription factor, glycosyltransferase, and wound-responsive family protein. The gene ontology term of carbohydrate metabolic process was significantly enriched in all anther stages, and many saccharides and starch synthase-related genes, such as invertase, sucrose synthase, and starch branching enzyme, were significantly different expressed in HS compared with CK. Furthermore, co-expression network analysis showed a module (midnightblue) strongly consistent with HS, and two hub genes (CsaV3_6G004180 and CsaV3_5G034860) were found with a high degree of connectivity to other genes. Our results provide comprehensive understandings on male flower development in cucumber under HS.

Responses of differential metabolites and pathways to high temperature in cucumber anther

“…Then, the germinated seeds were cultivated in plant pots and grown in a growth cabinet. When the cucumber plants formed the sixth true leaves, they were moved into a phytotron with 70% relative humidity under normal conditions (CK, 12 h at 28°C in the light/12 h at 25°C in the dark) or high-temperature (HT, 12 h at 38°C in the light/12 h at 30°C in the dark) stress (Chen et al, 2021b). These temperature treatments were stopped until we collected enough male flowers for observations of the anther structure and pollen fertility and for the metabolomics experiments.…”

“…The investigation of pollen fertility was performed as previously described (Chen et al, 2021b). The mature male flowers were obtained and quickly put in Carnoy's solution (ethanol:acetic acid = 3:1) for over 24 h, and they were kept in 70% ethanol after washing three times.…”

“…Therefore, the heatresistant abilities of male cucumber flowers need to be further explored in the future, which is of great significance for the improvement of breeding heat-resistant cucumber cultivars. Based on our previous research on the dynamic changes of gene expression on male cucumber flower development under hightemperature stress (Chen et al, 2021b), this study will use metabolomics to further explore the changes of metabolites in the mature pollen stage of cucumber, providing a new idea for research under normal growth conditions and high-temperature stress. The results will provide us a better understanding of how male cucumber flowers, especially its mature pollen, make a reaction at the metabolic level under high-temperature stress, as well as provide a theoretical foundation for heat-resistant cucumber breeding to minimize the damage caused by high-temperature stress.…”

QTL mapping reveals candidate genes for main agronomic traits in Luffa based on a high-resolution genetic map

“…The cucurbit model plant cucumber has been extensively studied to dissect the genetic architecture of important agronomic morphology (Pan et al, 2020a;Pan et al, 2020b;Chen et al, 2021;Shan et al, 2021). In addition to a large number of identified quantitative trait loci (QTLs) (Pan et al, 2020a;Wang et al, 2020), certain genes for corresponding traits, including fruit shape (Jiang et al, 2015;Xin et al, 2019;Zhao et al, 2019;Zhang et al, 2020b), inflorescence architecture (Wen et al, 2021), flowering time (Cai et al, 2020), plant height (Wang et al, 2017a) and stem diameter (Yang et al, 2022), have been characterized, which have considerably facilitated the genetic and molecular breeding of cucumbers.…”

Data_Sheet_1.pdf

“…Studies have shown that high temperature inhibits the growth and development of cucumber plants, as indicated by inhibited the bioaccumulation, decreased chlorophyll content, increased the lipid peroxidation level, delayed flowering, and appeared dropping flower and fruit (Zhou et al, 2016;Wang et al, 2018a;Chen et al, 2021b). Cucumber plants have evolved a series of physiological and molecular mechanisms in response to high temperature stress, such as increasing the content of proline, activating antioxidant defense system, inducing the expression of heat shock proteins, and regulating plant hormone signal pathways (Wei et al, 2019; April 2022 | Volume 13 | Article 883876 Li et al miR9748 Mediates Thermotolerance via JA He et al, 2020;Chen et al, 2021b). Furthermore, calcium signal, transcription factors, and post-transcription regulation also mediate cucumber high temperature stress tolerance (Zhou et al, 2013;Xu et al, 2015;Yu et al, 2018;Wang et al, 2018bWang et al, , 2020a.…”