HAK/KUP/KT family members have been identified as playing key roles in K⁺ uptake and salt tolerance in numerous higher plants. However, their functions in cassava (Manihot esculenta Cantz) remain unknown. In this study, a gene encoding for a high-affinity potassium transporter (MeHAK5) was isolated from cassava and its function was investigated. Subcellular localization analysis showed that MeHAK5 is a plasma membrane-localized transporter. RT-PCR and RT-qPCR indicated that MeHAK5 is predominantly expressed in cassava roots, where it is upregulated by low potassium or high salt; in particular, its highest expression levels separately increased by 2.2 and 2.9 times after 50 µM KCl and 150 mM NaCl treatments. When heterologously expressed in yeast, MeHAK5 mediated K⁺ uptake within the cells of the yeast strain CY162 and rescued the salt-sensitive phenotype of AXT3K yeast. MeHAK5 overexpression in transgenic Arabidopsis plants exhibited improved growth and increased shoot K⁺ content under low potassium conditions. Under salt stress, MeHAK5 transgenic Arabidopsis plants accumulated more K⁺ in the shoots and roots and had reduced Na⁺ content in the shoots. As a result, MeHAK5 transgenic Arabidopsis demonstrated a more salt-tolerant phenotype. These results suggest that MeHAK5 functions as a high-affinity K⁺ transporter under K⁺ starvation conditions, improving K⁺/Na⁺ homeostasis and thereby functioning as a positive regulator of salt stress tolerance in transgenic Arabidopsis. Therefore, MeHAK5 may be a suitable candidate gene for improving K⁺ utilization efficiency and salt tolerance.

The selection and breeding of salt-tolerant rice and the use of saline–alkali land for rice cultivation are crucial for food security. However, most studies have focused only on the seedling salt tolerance stage, with little research on the salt tolerance mechanisms during the reproductive growth period. This study selected the salt-tolerant rice line SR17, the salt-tolerant variety SR86, and the salt-sensitive variety IR29 as research subjects. Two salt stress gradients of 0% and 0.5% (7.8 dS m⁻¹) were established. Salt stress was applied continuously from rice transplanting to the maturity stage, and the differences in response mechanisms during the young panicle stage under long-term salt stress were analyzed. The results showed that, under salt stress, SR17 exhibited the least lipid peroxidation and membrane damage, followed by SR86, while IR29 suffered the most severe damage. SR17 and SR86 could reduce oxidative damage and maintain membrane system integrity by activating the antioxidant enzyme system and accumulating soluble proteins. In contrast, the antioxidant system in IR29 was insufficiently activated; this indicates that the adaptability of this variety to salt-induced oxidative stress is relatively poor. The chlorophyll content and most photosynthetic parameters in SR17 showed no significant changes, and leaf gas exchange performance and chlorophyll status were the least affected, whereas IR29 suffered severe damage. Agronomic trait investigation revealed that, compared with the control, SR17 exhibited the smallest reductions in plant height, spikelets per panicle, 1000-grain weight, grain yield per plant, and main spikelet number under salt stress, and the decreases in key yield-related indicators—effective panicle number, grain yield per plant, and seed setting rate—were not significant. This study confirms that SR17 possesses superior salt tolerance and holds potential for further breeding and multi-environment trials, while also providing an important basis for elucidating the physiological mechanisms of salt tolerance during the reproductive stage of rice.

Background: Xyloglucan endotransglucosylase/hydrolase (XTH) acts as a key cell wall-modifying enzyme and contributes to plant stress resilience. This study aimed to identify the MeXTH gene family in cassava and characterize its potential functions in abiotic stress adaptation. Method: A full set of bioinformatic analyses was performed, including phylogeny, gene structure, conserved motifs, chromosomal localization, synteny, promoter cis-elements and subcellular localization. Expression patterns were examined by quantitative real-time PCR (qRT-PCR). Results: Forty-two MeXTH genes were identified and distributed on 14 chromosomes, encoding proteins with conserved Glyco_hydro_16 (Glycoside hydrolase family 16) and XET_C (Xyloglucan endotransglycosylase C-terminal domain) domains. Genes were clustered into four subfamilies with similar structures. Synteny was closer between cassava and dicots than monocots. Twenty-four stress-, hormone- and light-related cis-elements were detected. Ten MeXTH genes showed obvious differential expression under stress, and most proteins were located in the cell wall. Conclusions: The MeXTH gene family is structurally conserved and can serve as a readout of abiotic stress in cassava. These results provide a theoretical basis for molecular breeding aimed at enhancing stress resistance in cassava.