Genome-Wide Analysis of Watermelon HSP20s and Their Expression Profiles and Subcellular Locations under Stresses

Abstract

Watermelon (Citrullus lanatus L.), which is an economically important cucurbit crop that is cultivated worldwide, is vulnerable to various adverse environmental conditions. Small heat shock protein 20s (HSP20s) are the most abundant plant HSPs and they play important roles in various biotic and abiotic stress responses. However, they have not been systematically investigated in watermelon. In this study, we identified 44 watermelon HSP20 genes and analyzed their gene structures, conserved domains, phylogenetic relationships, chromosomal distributions, and expression profiles. All of the watermelon HSP20 proteins have a conserved the α-crystallin (ACD) domain. Half of the ClHSP20s arose through gene duplication events. Plant HSP20s were grouped into 18 subfamiles and a new subfamily, nucleo-cytoplasmic XIII (CXIII), was identified in this study. Numerous stress- and hormone-responsive cis-elements were detected in the putative promoter regions of the watermelon HSP20 genes. Different from that in other species, half of the watermelon HSP20s were repressed by heat stress. Plant HSP20s displayed diverse responses to different virus infections and most of the ClHSP20s were generally repressed by Cucumber green mottle mosaic virus (CGMMV). Some ClHSP20s exhibited similar transcriptional responses to abscisic acid, melatonin, and CGMMV. Subcellular localization analyses of six selected HSP20- green fluorescence protein fusion proteins revealed diverse subcellular targeting. Some ClHSP20 proteins were affected by CGMMV, as reflected by changes in the size, number, and distribution of fluorescent granules. These systematic analyses provide a foundation for elucidating the physiological functions and biological roles of the watermelon HSP20 gene family.

Genome-Wide Characterization of the HSP20 Gene Family Identifies Potential Members Involved in Temperature Stress Response in Apple

“…In the present study, we identified 41 HSP20 genes and investigated their characteristics from the apple genome database. The number of apple HSP20 genes was higher than that of Arabidopsis (19) (Scharf et al, 2001), slightly higher than rice (39) (Ouyang et al, 2009) but lower than that of watermelon (44) (He et al, 2019), potato (48) (Zhao et al, 2018), and grape (48) (Ji et al, 2019). This difference is most likely due to the fact that apple had gene duplications during evolution (Velasco et al, 2010;Ma et al, 2018).…”

“…Plants have developed a series of physiological and molecular strategies to overcome temperature stress over evolutionary time ( Asea et al, 2016 ; Huo et al, 2020 ). Heat shock proteins (HSPs) are one of the strategies, and HSPs are essential in regulating growth, development and stress response in plants ( Waters et al, 1996 ; Wang et al, 2004 ; Asea et al, 2016 ; He et al, 2019 ).…”

“…Nineteen HSP20 genes have been identified in Arabidopsis ( Scharf et al, 2001 ), 39 in rice ( Ouyang et al, 2009 ), 42 in tomato ( Yu et al, 2016 ), 44 in watermelon ( He et al, 2019 ), and 48 in grape ( Ji et al, 2019 ). Previous studies have suggested that HSP20 genes are involved in regulating a diverse array of developmental processes and responses to abiotic stresses, especially in heat stress ( Guo et al, 2015 ; He et al, 2019 ; Ji et al, 2019 ). Yu et al (2016) identified tomato HSP20 family genes and analyzed their functions in abiotic-stress responses.…”

Genome-wide identification of small heat shock protein (HSP20) gene family in grape and expression profile during berry development

“…Members of the HSP20 gene family have been investigated in many plants, such as Arabidopsis, rice, soybean, watermelon, pepper and tomato. There are 19 HSP20 genes in Arabidopsis [11], 39 in rice [18], 51 in soybean [19], 44 in watermelon [20], 35 in pepper [21] and 42 in tomato [22]. To date, HSP20 gene family members of the grape have not been identified.…”

Genome-wide identification of small heat shock protein (HSP20) gene family in grape and expression profile during berry development

“…The number of Hsp20 genes in plants is about four times greater than that in animals [17]. For example , 19, 35, 39, 42, 44, 51 members of the Hsp20 gene family were respectively investigated in Arabidopsis (Arabidopsis thaliana) [11], pepper (Capsicum annuum L.) [18], rice (Oryza sativa) [19], tomato (Solanum lycopersicum) [20], watermelon (Citrullus lanatus L.) [21], and soybean (Glycine max) [22]. To date, Hsp20 gene family members in grape have not been identified.…”