HAK/KUP/KT family potassium transporter genes are involved in potassium deficiency and stress responses in tea plants (Camellia sinensis L.): expression and functional analysis

Abstract

Background Tea plant is one of the most important non-alcoholic beverage crops worldwide. While potassium (K + ) is an essential macronutrient and greatly affects the growth and development of plants, the molecular mechanism underlying K + uptake and transport in tea plant root, especially under limited-K + conditions, is still poorly understood. In plants, HAK/KUP/KT family members play a crucial role in K + acquisition and translocation, growth and development, and response to stresses. Nevertheless, the biological functions of these genes in tea plant are still in mystery, especially their roles in K + uptake and stress responses. Results In this study, a total of 21 non-redundant HAK/KUP/KT genes (designated as CsHAKs ) were identified in tea plant. Phylogenetic and structural analysis classified the CsHAKs into four clusters (I, II, III, IV), containing 4, 8, 4 and 5 genes, respectively. Three major categories of cis -acting elements were found in the promoter regions of CsHAKs . Tissue-specific expression analysis indicated extremely low expression levels in various tissues of cluster I CsHAKs with the exception of a high root expression of CsHAK4 and CsHAK5 , a constitutive expression of clusters II and III CsHAKs , and a moderate cluster IV CsHAKs expression. Remarkably, the transcript levels of CsHAKs in roots were significantly induced or suppressed after exposure to K + deficiency, salt and drought stresses, and phytohormones treatments. Also notably, CsHAK7 was highly expressed in all tissues and was further induced under various stress conditions. Therefore, functional characterization of CsHAK7 was performed, and the results demostrated that CsHAK7 locates on plasma membrane and plays a key role in K + transport in yeast. Taken together, the results provide promising candidate CsHAKs for further functional studies and contribute to the molecular breeding for new tea plants varieties with highly efficient utilization of K + . Conclusion This study demonstrated the first genome-wide analysis of CsHAK family genes of tea plant and provides a foundation for understanding the classification and functions of the CsHAKs in tea plants.

Transcriptome-wide identification and expression analysis of the KT/HAK/KUP family in Salicornia europaea L. under varied NaCl and KCl treatments

“…In addition, we found that the expression levels of some SeKUPs differed between shoots and roots, and that some SeKUPs were greatly suppressed under salt treatments. This is similar to Camellia sinensis ( CsHAK17 ) ( Yang et al, 2020 ), implying that they are not sensitive to high NaCl and K + deficiency.…”

Shading Promoted Theanine Biosynthesis in the Roots and Allocation in the Shoots of the Tea Plant (Camellia sinensis L.) Cultivar Shuchazao

“…The qRT-PCR was performed on a BioRad CFX96 real-time system, with a SYBR Green Master Mix kit (TaKaRa Biotechnology, Dalian, China), according to the manufacturer’s instructions. The components of the PCR mixture were as follows: 10 μL of 2× SYBR Premix ExTaq, 0.4 μL of each 10 μM forward and reverse primers, and 1 μL of the cDNA (150 ng) template, in 20 μL total volume . Three biological replicates of each sample were used, and the data are presented as mean ± standard error (SE) ( n = 3).…”

Potassium Control of Plant Functions: Ecological and Agricultural Implications

“…A crucial ecological aspect of K + is how plants can adapt to low-K-availability soils. Current experimental studies have observed that high-affinity K + transporters are mediators of K + stress responses [ 220 ]. Higher plants can adapt to drought stress by producing higher numbers and concentrations of amino acids and organic acids in the cell solution to replace the lack of K + for osmotic adjustment coupled with its negative effect on plant growth and reserve accumulation [ 213 ].…”

“…Recently, it has been found that the overexpression of several genes related to K + transporters and channels can increase the tolerance to K + deficiency. Among these, we can highlight the gene OsPRX2, which causes stomata closure [ 315 ]; the gene HAK, which is directly related to K + uptake under low soil K + availability [ 220 ]; or genes related to root elongation favoring higher K + uptake [ 316 ]. Thus, there is a great opportunity to genetically improve several crop species to improve potassium-use efficiency and help solve the problem of K + scarcity in soils and the access to potassium fertility in future markets [ 123 , 272 ].…”