Root development is a complex process involving phytohormones and transcription factors. Our previous research has demonstrated that BcWRKY33A is significantly expressed in Bok Choy roots under salt stress, and heterologous expression of BcWRKY33A increases salt tolerance and promotes root development in transgenic Arabidopsis. However, the precise molecular mechanisms by which BcWRKY33A governs root development remain elusive. Here, we investigated the role of BcWRKY33A in both root elongation and root hair formation in transgenic Bok choy roots. Our data indicated that overexpression of BcWRKY33A stimulated root growth and stabilized root hair morphology, while silencing BcWRKY33A prevented primary root elongation and resulted in abnormal root hairs morphology. Meanwhile, our research uncovered that BcWRKY33A directly binds to the promoters of BcLRP1 and BcCOW1, leading to an upregulation of their expression. In transgenic Bok choy roots, increased BcLRP1 and BcCOW1 transcript levels improved primary root elongation and root hair formation, respectively. Additionally, we pinpointed BcWRKY25 as a NaCl-responsive gene that directly stimulates the expression of BcWRKY33A in response to salt stress. All results shed light on the regulatory mechanisms governing root development by BcWRKY25-BcWRKY33A-BcLRP1/BcCOW1 module and propose potential strategies for improving salt tolerance in Bok choy.

The heat shock protein 70 (HSP70) family plays an important role in the growth and development of lettuce and in the defense response to high-temperature stress; however, its bioinformatics analysis in lettuce has been extremely limited. Genome-wide bioinformatics analysis methods such as chromosome location, phylogenetic relationships, gene structure, collinearity analysis, and promoter analysis were performed in the LsHSP70 gene family, and the expression patterns in response to high-temperature stress were analyzed. The mechanism of LsHSP70-19 in heat resistance in lettuce was studied by virus-induced gene silencing (VIGS) and transient overexpression techniques. The results showed that a total of 37 LsHSP70 genes were identified by the Hidden Markov Model (HMM) and Protein Family Database (Pfam). These 37 LsHSP70 genes were classified into groups A, B, C, and D by phylogenetic relationships. They were mainly localized on seven chromosomes except for chromosome 3; gene structure analysis showed that LsHSP70 contained 1–9 exons, and the protein structure domains of genes in the same group were highly conserved. The covariance analysis showed that nine pairs of LsHSP70 genes existed between LsHSP70 members, and lettuce LsHSP70 and sunflower HaHSP70 had been more conserved in the evolutionary process. The promoter analysis showed that there were a large number of cis-acting elements related to phytohormones, growth, development, stress, and light response in LsHSP70. In addition, the results of the expression pattern analysis for all LsHSP70 genes under high-temperature stress showed that 28 out of 37 LsHSP70 genes were able to respond to heat stress, and only LsHSP70-8, LsHSP70-14, LsHSP70-19, LsHSP70-23, and LsHSP70-24 were able to respond rapidly to heat stress (2 h). The expression of LsHSP70-19 was higher at different periods under high-temperature stress; the overexpression of LsHSP70-19, the plant fresh weight, and the root weight were better than the control (CK); and the heat resistance was better. These results suggest that LsHSP70-19 may play an important role under high-temperature stress in lettuce.

Biostimulants, particularly single amino acids, can increase plant growth and crop quality, gaining significant attention. This study investigates the effects of 10 amino acids via root/foliar application on the growth, quality, taste, and volatile flavor of mini-watermelons and compares the differences between the application methods. Here, we employed electronic noses, electronic tongues, and gas chromatography–ion mobility spectrometry to investigate these effects. Root application excels in fruit growth and pectin accumulation, while foliar application boosts soluble protein and specific nutrients. Specifically, root application (except for Val) significantly increases fruit weight, with Gly being most effective for longitudinal diameter, while most amino acids (except Val/Lys) promote transverse diameter. Pectin content shows bidirectional regulation: root application of Glu/Gly/Lys/Pro/Trp/Val enhances pectin, whereas foliar application inhibits it. For taste indices, most treatments improve soluble solids (except Glu root/Arg-Leu foliar), and Ala/Asp/Glu/Gly reduce titratable acids, optimizing the sugar–acid ratio. Foliar application is more efficient for soluble protein accumulation (Ala/Glu/Gly/Pro/Leu). For nutritional quality, except for Lys, all treatments increase vitamin C and widely promote total phenolics and lycopene, with only minor exceptions, and only Arg foliar application enhances ORAC. Additionally, the results revealed that root-applied lysine and valine greatly raised the levels of hexanal and 2-nonenal, whereas foliar-applied valine significantly increased n-nonanal and (Z)-6-nonenal. Overall, we found that amino acids can considerably improve mini-watermelon production, quality, taste, and antioxidant capacity, providing theoretical and practical references for their widespread use in agriculture.