Germin-like proteins (GLPs) are water-soluble plant glycoproteins belonging to the cupin superfamily. The important role of GLPs in plant responses against various abiotic and biotic stresses, especially pathogens, is well validated. However, little is known about cotton GLPs in relation to fungal pathogens. Here, a novel GLP gene was isolated from Gossypium hirsutum and designated as GhABP19 . The expression of GhABP19 was upregulated in cotton plants inoculated with Verticillium dahliae and Fusarium oxysporum and in response to treatment with jasmonic acid (JA) but was suppressed in response to salicylic acid treatment. A relatively small transient increase in GhABP19 was seen in H 2 O 2 treated samples. The three-dimensional structure prediction of the GhABP19 protein indicated that the protein has three histidine and one glutamate residues responsible for metal ion binding and superoxide dismutase (SOD) activity. Purified recombinant GhABP19 exhibits SOD activity and could inhibit growth of V. dahliae , F. oxysporum , Rhizoctonia solani , Botrytis cinerea , and Valsa mali in vitro . To further verify the role of GhABP19 in fungal resistance, GhABP19 -overexpressing Arabidopsis plants and GhABP19 -silenced cotton plants were developed. GhABP19-transgenic Arabidopsis lines showed much stronger resistance to V. dahliae and F. oxysporum infection than control (empty vector) plants did. On the contrary, silencing of GhABP19 in cotton conferred enhanced susceptibility to fungal pathogens, which resulted in necrosis and wilt on leaves and vascular discoloration in GhABP19 -silenced cotton plants. The H 2 O 2 content and endogenous SOD activity were affected by GhABP19 expression levels in Arabidopsis and cotton plants after inoculation with V. dahliae and F. oxysporum , respectively. Furthermore, GhABP19 overexpression or silencing resulted in activation or suppression of JA-mediated signaling, respectively. Thus, GhABP19 plays important roles in the regulation of resistance to verticillium and fusarium wilt in plants. These modulatory roles were exerted by its SOD activity and ability to activate the JA pathway. All results suggest that GhABP19 was involved in plant disease resistance.
Germin-like proteins (GLps) are a diverse and ubiquitous family of plant glycoproteins belonging to the cupin super family; they play considerable roles in plant responses against various abiotic and biotic stresses. Here, we provide evidence that GLP2 protein from cotton (Gossypium hirsutum) functions in plant defense responses against Verticillium dahliae, Fusarium oxysporum and oxidative stress. Purified recombinant GhGLP2 exhibits superoxide dismutase (SOD) activity and inhibits spore germination of pathogens. Virus-induced silencing of GhGLP2 in cotton results in increased susceptibility to pathogens, plants exhibited severe wilt on leaves, enhanced vascular browning and suppressed callose deposition. transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing GhGLP2 showed significant resistance to V. dahliae and F. oxysporum, with reduced mycelia growth, increased callose deposition and cell wall lignification at infection sites on leaves. The enhanced tolerance of GhGLP2-transgenic Arabidopsis to oxidative stress was investigated by methyl viologen and ammonium persulfate treatments, along with increased H 2 o 2 production. further, the expression of several defense-related genes (PDF1.2, LOX2, and VSP1) or oxidative stress-related genes (RbohD, RbohF) was triggered by GhGLP2. Thus, our results confirmed the involvement of GhGLP2 in plant defense response against Verticillium and Fusarium wilt pathogens and stress conditions. Cotton (Gossypium hirsutum L.) is an important fiber crop that is considered the backbone of the global fiber economy 1. Verticillium and Fusarium wilt are caused by Verticillium dahliae and Fusarium oxysporum, respectively, which are soil-borne pathogenic fungi that present major constraints to the production of cotton 2. Verticillium wilt is a notorious and devastating disease of cotton 3 , and it occurs before the squaring stage and peaks in the boll-setting stage, causing necrotic areas on the leaves, wilting, and discoloration of the vascular tissues 4. The disease symptoms of Fusarium wilt initiate and peak at the seedling and squaring stages, respectively, showing necrotic patches between the main veins and leaf detachment from the stem 5. Due to diverse factors, such as the climate, pathogen population structures, and cultivar susceptibility, the currently available control measures for these two diseases are not adequate 6. Thus, research on the cultivation of resistant cotton plants, by finding novel disease-resistant genes against these soil-borne fungal species, is consequently, of great importance. Previous studies have suggested that extracellular germins and germin-like proteins (GLPs) could be induced by a range of abiotic or biotic stresses, such as herbivores 7,8 , drought 9,10 , salinity 8,11 and they are considered to be the pathogenesis-related proteins (PRs) 16 family due to their disease resistance property 12-14. Germins and GLPs were first characterized in wheat (Triticum aestivum) and constitute a large plant gene family 15. They occur as water-solub...
Cotton is widely grown in many countries around the world due to the huge economic value of the total natural fiber. Verticillium wilt, caused by the soil-borne pathogen Verticillium dahliae, is the most devastating disease that led to extensive yield losses and fiber quality reduction in cotton crops. Developing resistant cotton varieties through genetic engineering is an effective, economical, and durable strategy to control Verticillium wilt. However, there are few resistance gene resources in the currently planted cotton varieties, which has brought great challenges and difficulties for breeding through genetic engineering. Further revealing the molecular mechanism between V. dahliae and cotton interaction is crucial to discovering genes related to disease resistance. In this review, we elaborated on the pathogenic mechanism of V. dahliae and the resistance mechanism of cotton to Verticillium wilt. V. dahliae has evolved complex mechanisms to achieve pathogenicity in cotton, mainly including five aspects: (1) germination and growth of microsclerotia; (2) infection and successful colonization; (3) adaptation to the nutrient-deficient environment and competition of nutrients; (4) suppression and manipulation of cotton immune responses; (5) rapid reproduction and secretion of toxins. Cotton has evolved multiple physiological and biochemical responses to cope with V. dahliae infection, including modification of tissue structures, accumulation of antifungal substances, homeostasis of reactive oxygen species (ROS), induction of Ca2+ signaling, the mitogen-activated protein kinase (MAPK) cascades, hormone signaling, and PAMPs/effectors-triggered immune response (PTI/ETI). This review will provide an important reference for the breeding of new cotton germplasm resistant to Verticillium wilt through genetic engineering.
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