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Introduction: Drought stress is one of the most serious abiotic stresses leading to crop yield reduction. Due to the wide range of planting areas, the production of maize is particularly affected by global drought stress. The cultivation of drought-resistant maize varieties can achieve relatively high, stable yield in arid and semi-arid zones and in the erratic rainfall or occasional drought areas. Therefore, to a great degree, the adverse impact of drought on maize yield can be mitigated by developing drought-resistant or -tolerant varieties. However, the efficacy of traditional breeding solely relying on phenotypic selection is not adequate for the need of maize drought-resistant varieties. Revealing the genetic basis enables to guide the genetic improvement of maize drought tolerance. Methods: We utilized a maize association panel of 379 inbred lines with tropical, subtropical and temperate backgrounds to analyze the genetic structure of maize drought tolerance at seedling stage. We obtained the high quality 7837 SNPs from DArT's and 91,003 SNPs from GBS, and a resultant combination of 97,862 SNPs of GBS with DArT's. The maize population presented the lower her-itabilities of the seedling emergence rate (ER), seedling plant height (SPH) and grain yield (GY) under field drought conditions. Results: GWAS analysis by MLM and BLINK models with the phenotypic data and 97862 SNPs revealed 15 variants that were significantly independent related to drought-resistant traits at the seedling stage above the threshold of P < 1.02 × 10-5. We found 15 candidate genes for drought resistance at the seedling stage that may involve in (1) metabolism (Zm00001d012176, Zm00001d012101, Zm00001d009488); (2) programmed cell death (Zm00001d053952); (3) transcriptional regulation (Zm00001d037771, Zm00001d053859, Zm00001d031861, Zm00001d038930, Zm00001d049400, Zm00001d045128 and Zm00001d043036); (4) autophagy (Zm00001d028417); and (5) cell growth and development (Zm00001d017495). The most of them in B73 maize line were shown to change the expression pattern in response to drought stress. These results provide useful information for understanding the genetic basis of drought stress tolerance of maize at seedling stage.
RESUMO
OBJECTIVE: This study aimed to probe into the diagnostic level and clinical value of ultrasound combined with enhanced MRI by Gd-BOPTA in hepatocellular carcinoma (HCC). METHODS: A total of 58 suspected HCC patients in our hospital from January 2016 to November 2020 were collected as the research subjects, including 37 HCC and 21 non-HCC patients. The diagnostic results of ultrasound and enhanced MRI by Gd-BOPTA were compared, and the microvascular invasion in patients was assessed. The independent risk factors of microvascular invasion were analyzed by logistics regression, and the diagnostic value of these factors was tested by ROC. RESULTS: The specificity, sensitivity and accuracy of enhanced MRI by Gd-BOPTA were 89.19%, 90.48% and 94.59%, respectively. The specificity, sensitivity and accuracy of ultrasound were 85.71%, 72.97% and 91.89%, and those of combined diagnosis were 76.19%, 97.30%, and 89.66%, respectively. The confirmation rate of microvascular invasion of enhanced MRI by Gd-BOPTA was dramatically higher than with ultrasound. Tumor diameter, comorbid cirrhosis and differentiation degree were independent risk factors of microvascular invasion, and ROC curve revealed that the area under the curve (AUC) of these risk factors was > 0.6. CONCLUSION: Enhanced MRI by Gd-BOPTA combined with ultrasound has good diagnostic value in HCC patients, and it can be widely used in early HCC diagnosis and clinical examination.
