Knockdown of Cytochrome P450 Genes Gh_D07G1197 and Gh_A13G2057 on Chromosomes D07 and A13 Reveals Their Putative Role in Enhancing Drought and Salt Stress Tolerance in Gossypium hirsutum.

Richard Odongo Magwanga,Xiaoyan Cai,Renhai Peng,Zhongli Zhou,Yuqing Hou,Pu Lu,Yanchao Xu,Joy Nyangasi Kirungu,Kunbo Wang,Stephen Gaya Agong,Xingxing Wang,Qi Dong,Liu Fang

doi:10.3390/genes10030226

Abstract

We identified 672, 374, and 379 CYPs proteins encoded by the CYPs genes in Gossypium hirsutum, Gossypium raimondii, and Gossypium arboreum, respectively. The genes were found to be distributed in all 26 chromosomes of the tetraploid cotton, with chrA05, chrA12, and their homeolog chromosomes harboring the highest number of genes. The physiochemical properties of the proteins encoded by the CYP450 genes varied in terms of their protein lengths, molecular weight, isoelectric points (pI), and even grand hydropathy values (GRAVY). However, over 99% of the cotton proteins had GRAVY values below 0, which indicated that the majority of the proteins encoded by the CYP450 genes were hydrophilic in nature, a common property of proteins encoded by stress-responsive genes. Moreover, through the RNA interference (RNAi) technique, the expression levels of Gh_D07G1197 and Gh_A13G2057 were suppressed, and the silenced plants showed a higher concentration of hydrogen peroxide (H2O2) with a significant reduction in the concentration levels of glutathione (GSH), ascorbate peroxidase (APX), and proline compared to the wild types under drought and salt stress conditions. Furthermore, the stress-responsive genes 1-Pyrroline–5-Carboxylate Synthetase (GhP5CS), superoxide dismutase (GhSOD), and myeloblastosis (GhMYB) were downregulated in VIGS plants, but showed upregulation in the leaf tissues of the wild types under drought and salt stress conditions. In addition, CYP450-silenced cotton plants exhibited a high level of oxidative injury due to high levels of oxidant enzymes, in addition to negative effects on CMS, ELWL, RLWC, and chlorophyll content The results provide the basic foundation for future exploration of the proteins encoded by the CYP450 genes in order to understand the physiological and biochemical mechanisms in enhancing drought and salt stress tolerance in plants.

Highlights

Cytochrome P450 (CYPs) is a diverse gene superfamily, often referred to as an ancient enzymatic system, with a wide distribution in plants and animals [1]
The number of proteins encoded by the cotton CYP540 genes were in agreement with previous findings in which a higher proportion of the CYP450 genes have been found to be abundant compared to other genes; for instance, in the model legume Medicago truncatula, a total of 151 putative CYP450 genes were identified, including 135 novel sequences [47]
The polypeptide lengths of the CYPs genes in the three cotton species varied; for instance, in G. hirsutum, the polypeptide lengths ranged from 51 aa to 2144 aa, molecular weights ranged from 5.95 kDa to 245.579 kDa, the isoelectric points was predicted to range from 4.153 to 10.971, and the grand average of hydropathy (GRAVY) ranged from −0.926 to 0.376

Summary

Introduction

Cytochrome P450 (CYPs) is a diverse gene superfamily, often referred to as an ancient enzymatic system, with a wide distribution in plants and animals [1]. Their number has exploded in plants [2]. The gene members of the cytochrome super family are coded with a CYP prefix, followed by a numeral for the family, a letter for the subfamily, and another numeral for the individual gene [5]. The P450 enzymes are believed to have evolved due to evolutionary adaptations as a result of metabolic and environmental changes in both plants and animals [3]

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