Potassium (K) plays a crucial role in multiple physiological and developmental processes in plants. Its deficiency is a common abiotic stress that inhibits plant growth and reduces crop productivity. A better understanding of the mechanisms involved in plant responses to low K could help to improve the efficiency of K use in plants. However, such responses remain poorly characterized in fruit tree species such as pears (Pyrus sp). We analyzed the physiological and transcriptome responses of a commonly used pear rootstock, Pyrus betulaefolia, to K-deficiency stress (0 mM). Potassium deprivation resulted in apparent changes in root morphology, with short-term low-K stress resulting in rapidly enhanced root growth. Transcriptome analyses indicated that the root transcriptome was coordinately altered within 6 h after K deprivation, a process that continued until 15 d after treatment. Potassium deprivation resulted in the enhanced expression (up to 5-fold) of a putative high-affinity K⁺ transporter, PbHAK5 (Pbr037826.1), suggesting the up-regulation of mechanisms associated with K⁺ acquisition. The enhanced root growth in response to K-deficiency stress was associated with a rapid and sustained decrease in the expression of a transcription factor, PbMYB44 (Pbr015309.1), potentially involved in mediating auxin responses, and the increased expression of multiple genes associated with regulating root growth. The concentrations of several phytohormones including indoleacetic acid (IAA), ABA, ETH, gibberellin (GA₃), and jasmonic acid (JA) were higher in response to K deprivation. Furthermore, genes coding for enzymes associated with carbon metabolism such as SORBITOL DEHYDROGENASE (SDH) and SUCROSE SYNTHASE (SUS) displayed greatly enhanced expression in the roots under K deprivation, presumably indicating enhanced metabolism to meet the increased energy demands for growth and K⁺ acquisition. Together, these data suggest that K deprivation in P. betulaefolia results in the rapid re-programming of the transcriptome to enhance root growth and K⁺ acquisition. These data provide key insights into the molecular basis for understanding low-K-tolerance mechanisms in pears and in other related fruit trees and identifying potential candidates that warrant further analyses.

The transcription factors (TFs) family known as the basic leucine zipper (bZIP) plays a vital role in a variety of biological processes. However, there is no investigation on the bZIP family in the major vegetable crop, eggplant. Here, a total of 71 SmbZIP genes were identified from the eggplant genome and compared with other 18 representative plants. According to the topology of the phylogenetic tree, as well as the categorization and nomenclature of bZIP genes in Arabidopsis and Solanum lycopersicum, the SmbZIP family was classified into 13 groups. Analysis of the chromosome location, motif composition and gene structure of the SmbZIP genes were also performed. Gene duplication analysis revealed that the expansion of the SmbZIP genes was mainly attributed to WGD/segmental duplication. Promoter analysis of the SmbZIP genes and examination of the expression patterns of SmbZIP genes under four abiotic pressures revealed that many SmbZIP genes are related to the control of abiotic stresses. Altogether, the identification, categorization, phylogenetic analysis, chromosome distribution, motif composition, and expression patterns of SmbZIPs were predicted and examined. Importantly, this investigation of SmbZIPs offers a wealth of information that will assist researchers in better understanding their function in eggplant.