Drought is one of the most important environmental constraints limiting plant growth and agricultural productivity. To understand the underlying mechanism of drought tolerance and to identify genes for improving this important trait, we conducted a gain-of-function genetic screen for improved drought tolerance in Arabidopsis thaliana. One mutant with improved drought tolerance was isolated and designated as enhanced drought tolerance1. The mutant has a more extensive root system than the wild type, with deeper roots and more lateral roots, and shows a reduced leaf stomatal density. The mutant had higher levels of abscisic acid and Pro than the wild type and demonstrated an increased resistance to oxidative stress and high levels of superoxide dismutase. Molecular genetic analysis and recapitulation experiments showed that the enhanced drought tolerance is caused by the activated expression of a T-DNA tagged gene that encodes a putative homeodomain-START transcription factor. Moreover, overexpressing the cDNA of the transcription factor in transgenic tobacco also conferred drought tolerance associated with improved root architecture and reduced leaf stomatal density. Therefore, we have revealed functions of the homeodomain-START factor that were gained upon altering its expression pattern by activation tagging and provide a key regulator that may be used to improve drought tolerance in plants.

Fruit shape and size are complex traits influenced by numerous factors, especially genetics and environment factors. To explore the mechanism of fruit shape and size development in cucumber, a pair of near-isogenic lines (NIL) Ln35 and Ln37 were used. The fruit length and diameter, cell length and diameter, and related gene expression were measured. Both the fruit length, diameter, and cell length and diameter showed sigmate curves in the two lines. The cell length and diameter were significantly positively correlated with fruit length and diameter both in two lines. The expression of CsACS2 and CsLNG showed significant positive correlations with fruit length and diameter increment in Ln35, and there was no correlation in Ln37. Furthermore, there were significant positive correlations between fruit size and thermal effectiveness (TE), as well as between fruit size and photosynthetic active radiation (PAR), both in two lines. Two models using logistic regression were formulated to assess the relationships among fruit length and diameter in Ln35 and Ln37, respectively, based on thermal effectiveness and photosynthetic active radiation (TEP). The coefficient R2 values of the models were 0.977 and 0.976 in Ln35, and 0.987 and 0.981 in Ln37, respectively. The root mean square error (RMSE) was 12.012 mm and 4.338 mm in Ln35, and 5.17 mm and 7.082 mm in Ln37, respectively, which illustrated the accurate and efficient of these models. These biologically interpreted parameters will provide precision management for monitoring fruit growth and forecasting the time of harvesting under different temperatures and light conditions.

Mutants are crucial to extending our understanding of genes and their functions in higher plants. In this study a spontaneous cucumber mutant, yf, showed yellow color leaves, had significant decreases in related physiological indexes of photosynthesis characteristics, and had more abnormal chloroplasts and thylakoids. Inheritance analysis indicated that the yellow color of the leaf was controlled by a recessive nuclear locus, yf. A candidate gene, CsSRP43, encoding a chloroplast signal recognition particle 43 protein, was identified through map-based cloning and whole-genome sequence analysis. Alignment of the CsSRP43 gene homologs between both parental lines revealed a 7-kb deletion mutation including the promoter region and the coding sequence in the yf mutant. In order to determine if the CsSRP43 gene was involved in the formation of leaf color, the CRISPR/Cas9-mediate system was used to modify CsSRP43 in the 9930 background; two independent transgenic lines, srp43-1 and srp43-2, were generated, and they showed yellow leaves with abnormal chloroplasts and thylakoids. Transcriptomic analysis revealed that differentially expressed genes associated with the photosynthesis-related pathway were highly enriched between srp43-1 and wild type, most of which were significantly downregulated in line srp43-1. Furthermore, yeast two-hybrid and biomolecular fluorescence complementation assays were used to confirm that CsSRP43 directly interacted with LHCP and cpSRP54 proteins. A model was established to explain the molecular mechanisms by which CsSRP43 participates in the leaf color and photosynthesis pathway, and it provides a valuable basis for understanding the molecular and genetic mechanisms of leaf color in cucumber.

Garlic (Allium sativum L.) is a popular condiment used as both medicine and food. Garlic production in China is severely affected by continuous cropping and is especially affected by leaf blight disease. Garlic is sterile, so it is very important to develop specialized genotypes, such as those for disease resistance, nutritional quality, and plant architecture, through genetic modification and innovation. In this experiment, we applied the induction method using EMS to mutate garlic cloves of cultivar G024. From the mutations, 5000 M0 mutants were generated and planted in the field. Then, 199 M1 mutant lines were screened according to growth potential and resistance to leaf blight. From M2 to M3, 169 generational lines were selected that grew well and were resistant to leaf blight in the field. Thereafter, their resistance to leaf blight was further analyzed in the lab; 21 lines resistant to leaf blight that had good growth potential were identified, among which 3 mutants were significantly different, and these were further screened. Also, transcriptome analysis of two mutants infected with Pleospora herbarum, A150 and G024, was performed, and the results revealed 2026 and 4678 differentially expressed genes (DEGs), respectively. These DEGs were highly enriched in hormone signaling pathway, plant–pathogen interaction, and MAPK signaling pathway. Therefore, the results provide a theoretical and technical basis for the creation of garlic germplasm resistant to leaf blight.