Abstract
BackgroundAuxins play an important role in plant growth and development; the auxins responsive gene; auxin/indole-3-acetic acid (Aux/IAA), small auxin-up RNAs (SAUR) and Gretchen Hagen3 (GH3) control their mechanisms. The GH3 genes function in homeostasis by the catalytic activities in auxin conjugation and bounding free indole-3-acetic acid (IAA) to amino acids.ResultsIn our study, we identified the GH3 genes in three cotton species; Gossypium hirsutum, Gossypium arboreum and Gossypium raimondii, analyzed their chromosomal distribution, phylogenetic relationships, cis-regulatory element function and performed virus induced gene silencing of the novel Gh_A08G1120 (GH3.5) gene. The phylogenetic tree showed four clusters of genes with clade 1, 3 and 4 having mainly members of the GH3 of the cotton species while clade 2 was mainly members belonging to Arabidopsis. There were no paralogous genes, and few orthologous genes were observed between Gossypium and other species. All the GO terms were detected, but only 14 genes were found to have described GO terms in upland cotton, more biological functions were detected, as compared to the other functions. The GH3.17 subfamily harbored the highest number of the cis-regulatory elements, most having promoters towards dehydration-responsiveness. The RNA expression analysis revealed that 10 and 8 genes in drought and salinity stress conditions respectively were upregulated in G. hirsutum. All the genes that were upregulated in plants under salt stress conditions were also upregulated in drought stress; moreover, Gh_A08G1120 (GH3.5) exhibited a significant upregulation across the two stress factors. Functional characterization of Gh_A08G1120 (GH3.5) through virus-induced gene silencing (VIGS) revealed that the VIGS plants ability to tolerate drought and salt stresses was significantly reduced compared to the wild types. The chlorophyll content, relative leaf water content (RLWC), and superoxide dismutase (SOD) concentration level were reduced significantly while malondialdehyde concentration and ion leakage as a measure of cell membrane stability (CMS) increased in VIGS plants under drought and salt stress conditions.ConclusionThis study revealed the significance of the GH3 genes in enabling the plant’s adaptation to drought and salt stress conditions as evidenced by the VIGS results and RT-qPCR analysis.
Highlights
Auxins play an important role in plant growth and development; the auxins responsive gene; auxin/ indole-3-acetic acid (Aux/indole-3acetic acid (IAA)), small auxin-up RNAs (SAUR) and Gretchen Hagen3 (GH3) control their mechanisms
The Pfam domain PF03321 was used as the query to obtain the GH3 proteins, 58, 38 and 36 GH3 proteins were identified in G. hirsutum, G. raimondii and G. arboreum, respectively, but after validating all the GH3 sequences through ScanProsite tool and simple modular architecture research tool (SMART) scan program as described by Yuan et al [19] in the identification of the GH3 proteins in Malus sieversii Roem
The proportions of the proteins encoded by the GH3 genes in the three cotton species, 58 (AD), 38 (D) and 36 (A), showed that there was an element of gene loss in either during the emergence of tetraploid cotton (AD), being the number of the proteins encoded by the GH3 genes were less than the sum total of either of the two diploid cotton species
Summary
Auxins play an important role in plant growth and development; the auxins responsive gene; auxin/ indole-3-acetic acid (Aux/IAA), small auxin-up RNAs (SAUR) and Gretchen Hagen (GH3) control their mechanisms. Despite the economic importance of cotton, its production has undergone a series of challenges and a decline due to the combined effects of abiotic and biotic stress factors [3]. In relation to abiotic stress factors such as drought, salt and extreme temperatures have continued to pose a challenge in cotton production, since they are region specific and purely regulated by the climatic conditions and human activities. Several stress responsive genes have been investigated in cotton and found to be effective in improving their adaptability, for instance, the late embryogenesis abundant (LEA) proteins [8], the NAC gene the cyclin dependent kinase (CDK) gene [9], G-protein-coupled receptors (GPCRs) gene [10], the multidrug and toxic compound extrusion (MATE) gene and the MYB genes [11], among others
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