Differential transcriptomic changes in low-potassium sensitive and low potassium tolerant tea plant (Camellia sinensis) genotypes under potassium deprivation

Potassium (K) deficiency is a common abiotic stress that can inhibit plant growth and thus reduce crop productivity. K shortages in tea farms are very severe in current tea production systems. Therefore, developing low-K tolerant tea plants is an effective approach to mitigating K deficiencies in agricultural production systems. Up to now, the mechanisms underlying the transcriptional changes of tea plants under K+ deprivation have not been studied. In this study, to elucidate the underlying mechanism of tea plant genotype tolerance to K deprivation, we investigated K deprivation-induced changes in root morphology and global transcription in two tea plant genotypes, 1511 and 1601, which are tolerant and sensitive to low-K conditions, respectively. The results showed that the root systems were more developed in 1511 than 1601. The K starvation treatment increased the proportion of roots with a 0.5-2 mm diameter in 1511 and the proportion of those with a 0-0.5 nun diameter in 1601. There were 487 and 294 up-regulated genes in 1511 and 1601 (> 2-fold change), respectively. The expression levels of the most differentially expressed genes in 1511 were higher than those in 1601. Under K+ starvation, we detected differentially expressed genes were only up-regulated in 1511 associated with ethylene-related, ammonium transporter, nitrate transporter, catalase-related and phosphatidylinositol-related pathways. These up-regulated genes might play crucial roles in root architecture and K+ uptake and utilization, which would help enhance the low-K tolerance of 1511. Our study provides new insights into the molecular mechanisms underlying tolerance of K+ starvation and builds a foundation for selecting low-K tolerance tea plant genotypes.