Transcriptome Analysis Unravels Key Factors Involved in Response to Potassium Deficiency and Feedback Regulation of K+ Uptake in Cotton Roots.

Doudou Yang,A Egrinya Eneji,Zhaohu Li,Fei Yi,Xiaoli Tian,Fangjun Li

doi:10.3390/ijms22063133

Doudou Yang, A Egrinya Eneji + Show 4 more

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https://doi.org/10.3390/ijms22063133

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Abstract

To properly understand cotton responses to potassium (K+) deficiency and how its shoot feedback regulates K+ uptake and root growth, we analyzed the changes in root transcriptome induced by low K+ (0.03 mM K+, lasting three days) in self-grafts of a K+ inefficient cotton variety (CCRI41/CCRI41, scion/rootstock) and its reciprocal grafts with a K+ efficient variety (SCRC22/CCRI41). Compared with CCRI41/CCRI41, the SCRC22 scion enhanced the K+ uptake and root growth of CCRI41 rootstock. A total of 1968 and 2539 differently expressed genes (DEGs) were identified in the roots of CCRI41/CCRI41 and SCRC22/CCRI41 in response to K+ deficiency, respectively. The overlapped and similarly (both up- or both down-) regulated DEGs in the two grafts were considered the basic response to K+ deficiency in cotton roots, whereas the DEGs only found in SCRC22/CCRI41 (1954) and those oppositely (one up- and the other down-) regulated in the two grafts might be the key factors involved in the feedback regulation of K+ uptake and root growth. The expression level of four putative K+ transporter genes (three GhHAK5s and one GhKUP3) increased in both grafts under low K+, which could enable plants to cope with K+ deficiency. In addition, two ethylene response factors (ERFs), GhERF15 and GhESE3, both down-regulated in the roots of CCRI41/CCRI41 and SCRC22/CCRI41, may negatively regulate K+ uptake in cotton roots due to higher net K+ uptake rate in their virus-induced gene silencing (VIGS) plants. In terms of feedback regulation of K+ uptake and root growth, several up-regulated DEGs related to Ca2+ binding and CIPK (CBL-interacting protein kinases), one up-regulated GhKUP3 and several up-regulated GhNRT2.1s probably play important roles. In conclusion, these results provide a deeper insight into the molecular mechanisms involved in basic response to low K+ stress in cotton roots and feedback regulation of K+ uptake, and present several low K+ tolerance-associated genes that need to be further identified and characterized.

Highlights

After 16 days, we observed that the interveinal chlorosis on the third and fourth leaves was more severe in self-grafts of CCRI41/CCRI41 than in reciprocal-grafts of
The biomass of roots, stem and leaves reduced to varying extents under K+ deficiency, and CCRI41/CCRI41 was impacted more strongly than SCRC22/CCRI41, especially in terms of root biomass (Figure 1d)
We identified several down-regulated genes related to ethylene in the roots of both CCRI41/CCRI41 and SCRC22/CCRI41 under low K+ condition, including one receptor gene GhERT, one GhEBF1/2 gene, and three GhERF1/2 genes

Summary

Introduction

Potassium (K+ ) is an essential macronutrient that plays crucial roles in plant growth, development, and response to stress, which include balancing the electrical charge of membranes, activating enzymes, transporting of minerals and metabolites, turgor regulation, osmoregulation, as well as signal transduction [1,2]. Potassium starvation can inhibit plant photosynthesis, reduce transpiration rate and stomatal conductance, affect carbohydrate translocation and metabolism, weaken resistance to biological and abiotic stresses, and decrease crop yield and quality [1,3]. Cotton (Gossypium hirsutum L.) is a potassium-sensitive crop due to its sparse roots and its relatively inefficient K+ absorption [3]. K+ availability in the soil is often limited which causes low-K+ stress during cotton growth periods [2,3]

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