Feifei Li

Nitrogen fertilizer application rate and storage duration are critical agronomic and environmental factors affecting rice quality stability. The milling appearance, eating and nutritional quality, physicochemical properties, microstructure, and volatile metabolic profiles during long-term storage were investigated using three indica-japonica hybrid cultivars at four nitrogen fertilizer application levels. High nitrogen fertilizer application (300 kg hm⁻²) promoted an over-filled protein matrix and induced structural defects such as micropores in starch granules, which acted as “trigger points” for accelerated aging. Specifically, storage duration was the dominant factor reshaping volatile profiles and lipid degradation, but high nitrogen amplified these effects by promoting lipid oxidation and the accumulation of off-flavor compounds. Correlation analysis revealed that gel consistency (GC) is a core determinant of eating quality, exhibiting significant negative correlations with amylose content, setback, hardness and fatty acid values, while showing positive correlations with peak viscosity, breakdown value, and adhesiveness. All correlation patterns collectively contributed to the deterioration of rice eating quality after storage, indicating GC might be served as an indirect indicator for evaluating rice deterioration and applied in the breeding of rice varieties with improved storage tolerance. Microstructural analysis via SEM high nitrogen induced distinct cultivar-specific deterioration characteristics after 12 months storage.

Chalkiness is a complex quantitative trait regulated by both genetic and environmental factors. Reducing chalkiness has long been a research focus in rice genetics and breeding. A total of 108 markers on/closely linked to starch biosynthesizing genes, grain shape and chalkiness QTLs were used to detect interactions affecting chalkiness. A total of 30 and 39 marker pairs with significant bigenic epistasis were identified for percentage of grain with chalkiness (PGWC) and degree of endosperm chalkiness (DEC), respectively, of which 16 were commonly found in both traits. Using markers associated with chalkiness and marker pairs with significant epistatic effects as candidate predictors increased the coefficient of determination (R²) of the best multiple regression models for predicting both traits. GBSSI, SSIIa and the interaction between GBSSI and GBSSII were consistently identified in optimal models, indicating their critical roles in regulating rice chalkiness. R² for DEC and PGWC ranged from 36.5% to 42.7% and from 52.9% to 73.8% in two environments, respectively. PGWC decreased significantly from 38.9% to 15.10% after three cycles using marker-assisted recurrent selection (MARS). This study suggests that epistasis contributes substantially to the regulation of chalkiness, and demonstrates that MARS can effectively improve chalkiness without imposing obvious negative impacts on eating quality.

Soil salinization is one of the abiotic stresses that inhibit plant growth and development, which seriously restricts global crop production. WRKY transcription factors play an important role in regulating plant responses to stress such as salt stress. In our previous study, two WRKY family genes from okra, AeWRKY32 and AeWRKY70, were significantly up-regulated and down-regulated, respectively, in response to salt stress. In this study, subcellular localization showed that they were localized to the nucleus. The down-regulation of AeWRKY32 and AeWRKY70 via whole plant virus-induced gene silencing (VIGS) increased and decreased plant sensitivity to salt stress, respectively. Ectopic expression of AeWRKY32 and AeWRKY70 led to promoted and reduced salt tolerance in transgenic Arabidopsis, respectively. There was no significant difference between transgenic plants and wild type (WT) without salt treatment. Salt stress significantly inhibited plant growth. The decrease of chlorophyll content and the increase of anthocyanin content in AeWRKY32-overexpressed transgenic plants were lower than those in the WT, while AeWRKY70-overexpressed plants had the opposite effect. Under salt stress, the AeWRKY70-overexpressed plants had the highest malondialdehyde (MDA) content, followed by the WT, and the lowest in AeWRKY32-overexpressed plants. The hydrogen peroxide (H₂O₂) content and superoxide anion (O₂^•−) generation rate were only slightly increased. Moreover, salt stress significantly increased plant proline content and antioxidant enzyme activities, which was highest in AeWRKY70-overexpressed plants except superoxide dismutase (SOD). Taken together, these results suggest that AeWRKY32 and AeWRKY70 play positive and negative roles in plant in response to salt stress, respectively.

OVATE family proteins (OFPs) play important roles in plant growth and development, hormone signaling, and stress response pathways. However, the functions of OsOFPs in rice are largely unknown. In this study, a novel gain-of-function rice mutant, Osofp6-D, was identified. This mutant exhibited decreased plant height, erect leaves, reduced panicle size, short and wide seeds, delayed seed germination time, and reduced fertility. These phenotypic changes were attributed to the increased expression of OsOFP6, which was caused by a T-DNA insertion. Complementation of the Osofp6-D phenotype by knockout of OsOFP6 using the CRISPR/Cas9 system confirmed that the Osofp6-D phenotype was caused by OsOFP6 overexpression. In addition, transgenic plants overexpressing OsOFP6 with the 35S promoter mimicked the Osofp6-D phenotype. Cytological observations of the glumes showed that OsOFP6 overexpression altered the grain shape, mainly by altering the cell shape. Hormone response experiments showed that OsOFP6 was involved in the gibberellin (GA) and brassinolide (BR) signaling responses. Further studies revealed that OsOFP6 interacts with E3BB, which is orthologous to the Arabidopsis central organ size-control protein BIG BROTHER (BB). This study further elucidates the regulation mechanism of the rice OFP family on plant architecture and grain shape.

Dynamic remodeling of the actin cytoskeleton plays a central role in the elongation of cotton fibers, which are the most important natural fibers in the global textile industry. Here, a high-resolution mapping approach combined with comparative sequencing and a transgenic method revealed that a G65V substitution in the cotton actin Gh_D04G0865 (GhACT17D in the wild-type) is responsible for the Gossypium hirsutum Ligon lintless-1 (Li₁) mutant (GhACT17DM). In the mutant GhACT17DM from Li₁ plant, Gly65 is substituted with valine on the lip of the nucleotide-binding domain of GhACT17D, which probably affects the polymerization of F-actin. Over-expression of GhACT17DM, but not GhACT17D, driven by either a CaMV35 promoter or a fiber-specific promoter in cotton produced a Li₁-like phenotype. Compared with the wild-type control, actin filaments in Li₁ fibers showed higher growth and shrinkage rates, decreased filament skewness and parallelness, and increased filament density. Taken together, our results indicate that the incorporation of GhACT17DM during actin polymerization disrupts the establishment and dynamics of the actin cytoskeleton, resulting in defective fiber elongation and the overall dwarf and twisted phenotype of the Li₁ mutant.

Background: In plants, sucrose synthase (Sus) is widely considered as a key enzyme involved in sucrose metabolism. Several paralogous genes encoding different isozymes of Sus have been identified and characterized in multiple plant genomes, while limited information of Sus genes is available to date for cotton. Results: Here, we report the molecular cloning, structural organization, phylogenetic evolution and expression profiles of seven Sus genes (GaSus1 to 7) identified from diploid fiber cotton (Gossypium arboreum). Comparisons between cDNA and genomic sequences revealed that the cotton GaSus genes were interrupted by multiple introns. Comparative screening of introns in homologous genes demonstrated that the number and position of Sus introns are highly conserved among Sus genes in cotton and other more distantly related plant species. Phylogenetic analysis showed that GaSus1, GaSus2, GaSus3, GaSus4 and GaSus5 could be clustered together into a dicot Sus group, while GaSus6 and GaSus7 were separated evenly into other two groups, with members from both dicot and monocot species. Expression profiles analyses of the seven Sus genes indicated that except GaSus2, of which the transcripts was undetectable in all tissues examined, and GaSus7, which was only expressed in stem and petal, the other five paralogues were differentially expressed in a wide ranges of tissues, and showed development-dependent expression profiles in cotton fiber cells. Conclusions: This is a comprehensive study of the Sus gene family in cotton plant. The results presented in this work provide new insights into the evolutionary conservation and sub-functional divergence of the cotton Sus gene family in response to cotton fiber growth and development.