AUTHOR=Shiraku Margaret L. , Magwanga Richard Odongo , Cai Xiaoyan , Kirungu Joy Nyangasi , Xu Yanchao , Mehari Teame Gereziher , Hou Yuqing , Wang Yuhong , Agong Stephen Gaya , Peng Renhai , Wang Kunbo , Zhou Zhongli , Liu Fang 

TITLE=Functional Characterization of GhACX3 Gene Reveals Its Significant Role in Enhancing Drought and Salt Stress Tolerance in Cotton

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.658755

DOI=10.3389/fpls.2021.658755

ISSN=1664-462X

ABSTRACT=Acyl-coenzyme A oxidase 3 (ACX3) gene involved in β-oxidation pathway plays a critical role in plant growth and development as well as the stress response. Earlier on, studies focused primarily on the role of β-oxidation limited to fatty acid breakdown. However, ACX3 peroxisomal β-oxidation pathways result in a downstream cascade that acts as transduction of biochemical and physiological responses to stress. A role that is yet to be studied extensively. In this study, we identified 20, 18, 22, 23, 20, 11 and 9 proteins in G. hirsutum, G. barbadense, G. tomentosum, G. mustelinum, G. darwinii, G. arboreum and G. raimondii genomes. The tetraploid cotton genome had protein ranging between 18 and 22, while diploid were 9 and 11. After analyzing the gene family evolution or selection pressure, the gene family undergoes purely segmental duplication both in diploids and tetraploids. W-Box (WRKY-binding site), ABRE, CAAT–Box, TATA-box, MYB, MBS, LTR, TGACG and CGTCA-motif are abiotic stress Cis-regulatory elements identified in this gene family. All these are the binding sites for abiotic stress transcription factors, indicating that this gene is essential. Genes found in G.hirsutum showed a clear response to drought and salinity stress, with higher expression under drought and salt stress, particularly in the leaf and root, according to expression analysis. We selected Gh_DO1GO186 one of the genes highly expressed for functional Wecharacterization. We functionally characterized the GhACX3 gene through overexpression and VIGS. Overexpression of this gene enhanced tolerance under stress, which was exhibited by the germination assay. The overexpressed seed growth rate was faster relative to control under drought and salt stress conditions. The survival rate was also higher in overexpressed plants relative to control plants under stress. In contrast, the silencing of the GhACX3 gene in cotton plants resulted in plants showing stress susceptibility phenotype and reduced root length compared to control. Biochemical analysis also demonstrated that GhACX3 silenced plants experienced oxidative stress while the overexpressed plants did not. Besides, expression analysis showed that this gene is highly expressed in the roots. This study has revealed the importance of the ACX3 family during stress tolerance and can breed stress-resilient cultivar.