Salt stress can significantly affect plant growth and agricultural productivity. Receptor-like kinases (RLKs) are believed to play essential roles in plant growth, development, and responses to abiotic stresses. Here, we identify a receptor-like cytoplasmic kinase, salt tolerance receptor-like cytoplasmic kinase 1 (STRK1), from rice () that positively regulates salt and oxidative stress tolerance. Our results show that STRK1 anchors and interacts with CatC at the plasma membrane via palmitoylation. CatC is phosphorylated mainly at Tyr-210 and is activated by STRK1. The phosphorylation mimic form CatC exhibits higher catalase activity both in vitro and in planta, and salt stress enhances STRK1-mediated tyrosine phosphorylation on CatC. Compared with wild-type plants, -overexpressing plants exhibited higher catalase activity and lower accumulation of HO as well as higher tolerance to salt and oxidative stress. Our findings demonstrate that STRK1 improves salt and oxidative tolerance by phosphorylating and activating CatC and thereby regulating HO homeostasis. Moreover, overexpression of in rice not only improved growth at the seedling stage but also markedly limited the grain yield loss under salt stress conditions. Together, these results offer an opportunity to improve rice grain yield under salt stress.

Traditional transformation methods are complex and time consuming. It is generally difficult to transform indica rice varieties using traditional transformation methods due to their poor regeneration. In this contribution, a simple method was developed for the transformation of indica rice. In this method, the mature embryos of soaked seeds were pierced by a needle, and then soaked in the Agrobacterium inoculum under vacuum infiltration. The inoculated seeds germinated and grew to maturation (T (0)) under nonsterile conditions. The herbicide or antibiotic analysis and molecular analysis were conducted on T (0) plants. The results showed that although the efficiency of transformation was about 6.0%, it was easier to transform indica rice using the proposed method, and the transformation process was significantly shortened. The success of transformation was further confirmed by the genetic and molecular analyses of T (1) transformants.

Double B-box 1a (DBB1a) belongs to the zinc-finger family proteins in Arabidopsis thaliana. Transcriptional analysis uncovered that the DBB1a gene expression was blue light-dependently regulated, and the transcript level of DBB1a in cry1cry2 was decreased but not in phyAphyB compared to wild type under blue light conditions. Transgenic plants containing pDBB1a:GUS (β-glucuronidase) displayed GUS activity in the vascular system of leaves and petioles. Green fluorescent protein (GFP)-fused DDB1a (DBB1a-GFP) protein was found in the nucleus in transient transformation assays with onion epidermal cells as well as in stable transgenic Arabidopsis plants. To investigate the function of DBB1a, we generated DBB1a over-expressing and under-expressing transgenic Arabidopsis plants. Analysis of hypocotyl growth of these lines indicated that DBB1a promoted hypocotyl elongation under blue light condition. The phenotype of transgenic plants with DBB1a over-expression could be impaired by a gibberellin (GA)-biosynthesis inhibitor. Moreover, the expression analysis of GA metabolic and catabolic genes in DBB1a transgenic lines indicated that the DBB1a suppressed GA2-oxidase1 (GA2ox1) and GA2-oxidase8 (GA2ox8) expression, but induced GA3β-hydroxygenase1 (GA3ox1) and GA20-oxidase1 (GA20ox1) expression under blue light. Taken together, we concluded that DBB1a promotes hypocotyl elongation under blue light condition through an increase in bioactive GA levels in Arabidopsis.

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Lectin receptor-like kinases (LecRK) are widespread in higher plants; however, little is known about their physiological roles. In this study, At1g70130 (designated LecRK-b2), an Arabidopsis LecRK gene, has been investigated. LecRK-b2 was predominantly expressed during seed germination, and its expression was ceased following germination. The expression of LecRK-b2 was induced by abscisic acid (ABA), salt, and osmotic stress. LecRK-b2 lossof-function mutation slightly reduced the ABA sensitivity during seed germination, and this reduced sensitivity was demonstrated not due to lower ABA accumulation level in the seeds. Dual-luciferase transient expression assay confirmed that the transcription factor ABSCISIC ACID INSENSITIVE3 (ABI3) could activate the luciferase under driving of LecRK-b2 promoter. LecRK-b2 transcription level was found to be down-regulated in abi3 during seed germination. Furthermore, LecRK-b2 loss-of-function mutation reduced the salt and osmotic sensitivity during early development stage of Arabidopsis. Taken together, these results suggest that LecRK-b2 functions as a positive regulator of the ABA response during the seed germination and is involved in salt and osmotic stress response in the early development stage.