Salinity tolerance is an important physiological index for crop breeding.  Roots are typically the first plant tissue to withstand salt stress.  In this study, we found that the tomato (Solanum lycopersicum) trehalose-6-phosphate phosphatase (SlTPP4) gene is induced by abscisic acid (ABA) and salt, and is mainly expressed in roots.  Overexpression of SlTPP4 in tomato enhanced tolerance to salt stress, resulting in better growth performance.  Under saline conditions, SlTPP4 overexpression plants demonstrated enhanced sucrose metabolism, as well as increased expression of genes related to salt tolerance.  At the same time, expression of genes related to ABA biosynthesis and signal transduction was enhanced or altered, respectively.  In-depth exploration demonstrated that SlTPP4 enhances Casparian band development in roots to restrict the intake of Na⁺.  Our study thus clarifies the mechanism of SlTPP4-mediated salt tolerance, which will be of great importance for the breeding of salt-tolerant tomato crops.

Various genetic and biochemical characteristics exist in tea plant cultivars, and they largely determine production suitability and tea quality.  Here, we performed transcriptomic and metabolomic analyses of young shoots of seven tea cultivars and identified major regulatory transcription factors (TFs) for the characteristic metabolites in different cultivars based on weighted gene co-expression network analysis (WGCNA).  Phenotypically, we found that ‘Tieguanyin’ (TGY) and ‘Fujian Shuixian’ (FJSX), which are suitable for oolong tea, had higher catechin contents.  The metabolites of ‘Jinxuan’ (JX) were more prominent, especially the contents of phenolic acids, flavonoids, terpenes, and tannins, which were higher than those of the other six cultivars.  Moreover, ‘Fudingdabai’ (FDDB), which is suitable for white tea, was rich in amino acids, linolenic acid, and saccharides.  At the molecular level, hydroxycinnamoyl CoA quinate hydroxycinnamoyl transferase (HCT) (CsTGY12G0001876, and CsTGY06G0003042) led to the accumulation of chlorogenic acid in TGY.  The main reason for the higher l-ascorbic acid content in FJSX was the high expression levels of L-galactono-1,4-lactone hydrogenase (GalLDH) (CsTGY13G0000389) and Myo-inositol oxygenase (MIOX) (CsTGY14G0001769, and CsTGY14G0001770), which were regulated by WRKY (CsTGY11G0001197).  Furthermore, FDDB, ‘Longjing 43’ (LJ43), ‘Shuchazao’ (SCZ)  and ‘Baihaozao’ (BHZ) had higher free fatty acid contents, among which MYB (CsTGY14G0002344) may be a hub gene for the regulation of palmitoleic acid accumulation.  More importantly, we found that the shoots of TGY were green with purple, mainly due to the accumulation of anthocyanins and the downregulation of the Mg-protoporphyrin IX nonomethyl ester cyclase (MPEC) (CsTGY10G0001989) gene that affects chlorophyll synthesis.  These results will provide a theoretical reference for tea cultivar breeding and suitability.

The tetracycline (Tet)-off gene expression regulation system based on the TetR-VP16/Top10 construct has not been widely utilized in plants, for its highly expressed TetR-VP16 activator is toxic to some plants and repeatedly replenishing tetracycline to turn off the constitutively active system is a tedious process.  To solve these problems, a Tet-off and heat shock (HS)-on gene expression regulation system was constructed in this study.  This system is composed of a chimeric transactivator gene TetR-HSF that is derived from a Tet repressor (TetR) and a HS transcription factor (HSF) controlled by a HS promoter HSP70m, and a Tet operator containing hybrid promoter, Om35S, that drives expression of the β-glucuronidase (GUS) gene.  The resultant system yields a GUS expression pattern similar to that of the HSP70m promoter under inducing temperatures and at 35 and 40°C drives GUS expression to a similar level as the Cauliflower mosaic virus (CaMV) 35S promoter.  Further examination revealed that the TetR-HSF and GUS genes were induced by HS, reaching peak expression after 1 and 6 h treatment, respectively, and the HS induction of the expression system could be inhibited by Tet.  This system will provide a useful tool for transgenic studies of plants in the laboratory and in the field, including transgene function analysis, agronomic trait improvement, biopharmaceutical protein production and others.

Leaf rolling is an important morphological trait in wheat (Triticum aestivum L.), strongly correlating to photosynthesis, transpiration, and respiration, especially in abiotic stress conditions.  Identification of quantitative trait loci (QTLs)/genes underling rolling leaf is essential for wheat breeding.  In this study, one EMS-induced mutant Y536 was isolated in Nongda3753 background with extreme abaxial rolling leaf.  The F₂ and F_2:3 populations derived from a cross between Jing411 and mutant Y536 with contrasting leaf rolling morphology were developed to map locus controlling leaf rolling.  A public SSR marker was isolated on chromosome 6DL that held a high linkage level with leaf rolling index (LRI).  Quantitative trait locus (QTL) analysis revealed a stable QTL associated with LRI, named QLRI.cau-6D, which explained 7.69 to 10.86% of the total phenotypic variation and had LOD scores ranging from 10.00 to 13.32.  TraesCS6D02G237000 (TaHDZIV-D1) was the priority candidate gene according to coding sequence differences between two parents and gene functional annotations.  Consistently, knockout of TaHDZIV-A1/B1/D1 in common wheat line ‘JW1’ significantly increased LRI compared to the wild type, as well as overexpression of TaHDZIV-D1 in ‘JW1’ significantly decreased LRI until opposite direction.  Moreover, genetic evidence suggested that a dose-dependent manner in TaHDZIV-A1/B1/D1 affects leaf rolling.  Collectively, these findings provide a novel and recent insight into the genetic base of leaf rolling in common wheat.