Employing template-directed CRISPR-based editing of the OsALS gene to create herbicide tolerance in Basmati rice.

Rice (Oryza sativa) is one of the primary food crops which contributes major portion of daily calorie intake. It is used as model crop for various genome editing studies. Basmati rice was also explored for establishing non-homologous end joining-based genome editing. But it was not clear whether homology-directed repair (HDR)-based genome editing can be done in Basmati rice. The current study was designed to establish HDR-based genome editing in Basmati rice to develop herbicide tolerance. There is severe weed spread when rice is grown via direct planted rice method in various countries to save labour and water resources. Therefore, the use of herbicides is necessary to control weeds. These herbicides can also affect cultivated rice which creates the need to develop herbicide-tolerant rice. In current study, we introduced a point mutation in Acetolactate Synthase gene to convert tryptophan to leucine at position 548. For this purpose, different constructs for HDR were tested with different RNA scaffold and orientation of repair templates. Out of four different architectures, the one having repair template identical to the target DNA strand precisely edited the target site. We successfully established template-directed CRISPR-Cas9 system in Super Basmati rice by detecting desired substitutions at the target site in Acetolactate Synthase locus. Moreover, this editing of Acetolactate Synthase gene resulted in the production of herbicide tolerance in Super Basmati rice. This study suggests that such type of HDR system can be used to precisely edit other genes for crop improvement.

Precise CRISPR-Cas9 Mediated Genome Editing in Super Basmati Rice for Resistance Against Bacterial Blight by Targeting the Major Susceptibility Gene.

Basmati rice is famous around the world for its flavor, aroma, and long grain. Its demand is increasing worldwide, especially in Asia. However, its production is threatened by various problems faced in the fields, resulting in major crop losses. One of the major problems is bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo). Xoo hijacks the host machinery by activating the susceptibility genes (OsSWEET family genes), using its endogenous transcription activator like effectors (TALEs). TALEs have effector binding elements (EBEs) in the promoter region of the OsSWEET genes. Out of six well-known TALEs found to have EBEs in Clade III SWEET genes, four are present in OsSWEET14 gene's promoter region. Thus, targeting the promoter of OsSWEET14 is very important for creating broad-spectrum resistance. To engineer resistance against bacterial blight, we established CRISPR-Cas9 mediated genome editing in Super Basmati rice by targeting 4 EBEs present in the promoter of OsSWEET14. We were able to obtain four different Super Basmati lines (SB-E1, SB-E2, SB-E3, and SB-E4) having edited EBEs of three TALEs (AvrXa7, PthXo3, and TalF). The edited lines were then evaluated in triplicate for resistance against bacterial blight by choosing one of the locally isolated virulent Xoo strains with AvrXa7 and infecting Super Basmati. The lines with deletions in EBE of AvrXa7 showed resistance against the Xoo strain. Thus, it was confirmed that edited EBEs provide resistance against their respective TALEs present in Xoo strains. In this study up to 9% editing efficiency was obtained. Our findings showed that CRISPR-Cas9 can be harnessed to generate resistance against bacterial blight in indigenous varieties, against locally prevalent Xoo strains.

Genome Editing Technologies for Rice Improvement: Progress, Prospects, and Safety Concerns.

Rice (Oryza sativa) is an important staple food crop worldwide; to meet the growing nutritional requirements of the increasing population in the face of climate change, qualitative and quantitative traits of rice need to be improved. Stress-tolerant crop varieties must be developed with stable or higher yields under stress conditions. Genome editing and speed breeding have improved the accuracy and pace of rice breeding. New breeding technologies including genome editing have been established in rice, expanding the potential for crop improvement. Recently, other genome editing techniques such as CRISPR-directed evolution, CRISPR-Cas12a, and base editors have also been used for efficient genome editing in rice. Since rice is an excellent model system for functional studies due to its small genome and close syntenic relationships with other cereal crops, new genome-editing technologies continue to be developed for use in rice. In this review, we focus on genome-editing tools for rice improvement to address current challenges and provide examples of genome editing in rice. We also shed light on expanding the scope of genome editing and systems for delivering homology-directed repair templates. Finally, we discuss safety concerns and methods for obtaining transgene-free crops.

Oxidative stress-induced DNA damage and homocysteine accumulation may beinvolved in ovarian cancer progression in both young and old patients.

BACKGROUND/AIM: Biochemical, environmental, and genetic factors such as oxidative stress-induced DNA damage and homocysteine (Hcy) accumulation in the blood are involved in the development and progression of ovarian cancer. This study measured some biomarkers closely linked to the progression of ovarian cancer and also found their correlates. MATERIALS AND METHODS: Thirty patients were diagnosed with ovarian cancer using pelvic examination, transvaginal ultrasound, and cancer antibody (CA-125) measurement. Total oxidative stress (TOS), DNA damage, Hcy, malondialdehyde (MDA), total antioxidant status (TAS), and other biochemical parameters were determined. RESULTS: TOS and DNA damage were positively and significantly correlated between themselves and were involved in causation of tumors as reflected by significantly (P < 0.001) higher CA-125, erythrocyte sedimentation rate (ESR), creatinine, and C-reactive protein (CRP) in both young and old patients. Both were significantly correlated with Hcy, LDL-cholesterol, alanine aminotransferase, aspartate aminotransferase, CRP, MDA, and CA-125. However, they were negatively correlated with TAS. Thus, excessive inflammation and oxidative stress caused an increase in DNA damage and enhanced Hcy content, leading to development of ovarian cancer. CONCLUSION: This study suggests the use of antioxidants as drugs to reduce oxidative stress, DNA damage, and other causes of cancer development.