OsSPL transcription factor plays an important role in the development and stress response of rice (Oryza sativa) roots, leaves, floral organs, and ears. In this study, the OsSPL3 promoter was analyzed to explore the expression pattern of OsSPL3 transcription factor in rice and its response to drought stress. The Cis-acting elements in the OsSPL3 promoter region were analyzed by PLACE and Plant CARE online softwares, and the recombinant expression vector of OsSPL3 promoter and β-glucuronidase(GUS) gene was constructed, which was transformed into ZH11 rice callus, and positive transgenic plants were obtained by screening. The GUS expression activity of pOsSPL3-GUS transgenic plants and the expression patterns under drought stress and abscisic acid (ABA) treatments were detected. The results of promoter analysis showed that in addition to the necessary transcription initiation core elements and light-responsive elements, the OsSPL3 promoter region also included three MYB-involved drought-inducible elements, three gibberellin-responsive elements, two anaerobic induction essential elements, one low temperature response element, one endosperm expression regulatory element, one zein metabolism regulatory element and one meristem expression-related regulatory element. The results of GUS staining showed that the expression activity of GUS gene in young leaves, stem sheaths, coleoptiles and other young tissues was high, as well as in the vigorous growth parts of roots such as root cap, meristem zone, and elongation zone. In addition, the drought stress could significantly enhanced the GUS activity of transgenic rice leaves and roots. It shows that OsSPL3 transcription factor plays a regulatory role in the process of coleoptile growth, new leaf formation, root extension and stem sheath elongation after seed germination, and OsSPL3 transcription factor is also involved in the response process of rice drought stress.
In order to demonstrate the mechanism of promoting crop growth by the well-cellar style transplanting (WCST), this study analyzed the physiological, biochemical and transcriptomic characteristics of tobacco seedlings under WCST compared with the conventional transplanting (CT), in which seedlings were transplanted on membranes. The results showed that under WCST, the average air temperature and average relative humidity of the atmosphere were 22.29 ℃ and 97.10%, enhanced by 4.76 ℃ and 58.97% compared with CT, respectively. However, the average photosynthetically active radiation (PAR) was 221.57 μmol/(m2·s), reduced by 20.53% than CT. After transplanting, the plant height and maximum leaf area under WCST were significantly improved, and the leaf water potential was enhanced between 29.92% and 64.46%. Furthermore, superoxide dismutase (SOD), peroxidase (POD) activities and malonaldehyde (MDA) content were reduced by 14.48%, 8.86%, and 9.83% compared with CT (P＜0.05), respectively. There were 4 845 differentially expressed genes (DEGs) identified, including 2 693 down-regulated genes and 2 152 up-regulated genes according to transcriptome sequencing. Some down-regulated DEGs are significantly enriched in “oxidation-reduction process” and “oxidoreductase activity” according to gene ontology (GO) annotation. Some DEGs involved in “flavonoid biosynthesis” are significantly enriched according to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. WCST decreased the gene expressions of chalcone isomerase, flavanone-3-hydroxylase,flavonol synthase,flavonoid-3′-hydroxylase,andflavonol-3-O-glucoside L-rhamnosyltransferaserelated with flavonoid biosynthesis, and significantly reduced the contents of the dihydroquercetin, rutin, kaempferol-3-O-glucoside, quercetin-3-O-galactoside, luteolin, isorhamnetin-3-O-rutinoside and kaempferol-3-O-rutinoside. The higher air temperature, air relative humidity and lower PAR were beneficial to the growth and development of tobacco seedlings under WCST, which avoiding the adverse stress.
