超高压处理对谷氨酰胺转氨酶诱导的大豆分离蛋白凝胶冻融稳定性影响研究

为探索提高谷氨酰胺转氨酶(transglutaminase,TG酶)诱导的大豆分离蛋白凝胶冻融稳定性的方法,分析超高压处理对其作用效果,采用粒径、内源性荧光光谱、傅里叶红外变换光谱分析大豆分离蛋白的结构变化,并分析冻融循环过程中的可溶性蛋白含量、水分分布状态、持水性、质构特性、微观结构、流变特性,探讨作用机理。结果表明:未经超高压处理的TG酶诱导大豆分离蛋白凝胶,随着冻融次数增加,可溶性蛋白含量和凝胶持水性呈降低趋势,凝胶硬度呈上升趋势,凝胶微观结构孔缝较大,说明凝胶品质发生劣变;经过超高压处理的TG酶诱导大豆分离蛋白凝胶与未经过超高压处理凝胶相比,持水性、硬度呈先增加后下降趋势。当压力处理为400 MPa时,经5次冻融循环后SPI凝胶硬度和结合水含量较未冻融样品分别增高了140.43 g和30.019,持水性和可溶性蛋白含量分别降低了38.67%和7.87%。由此证明超高压处理是提高TG酶诱导的大豆分离蛋白凝胶冻融稳定性的有效方法。

南瓜、黄瓜和油菜幼苗对镉胁迫的响应

为了评估镉对瓜菜生长发育的影响,以南瓜、黄瓜和油菜为试验材料,用不同浓度镉离子溶液(0、1、10、100 mg·L^-1)进行处理,测定其生长发育指标及抗氧化活性。结果表明,与对照相比,100 mg·L^-1镉处理南瓜幼苗的根长、茎长、根鲜质量、地上鲜质量和叶片POD活性,黄瓜幼苗的根长和根鲜质量,油菜幼苗的根长、茎长、根鲜质量、地上鲜质量和叶片MDA含量分别降低了91.64%、16.72%、84.23%、46.22%、71.49%、86.87%、86.16%、91.99%、32.46%、83.53%、54.97%和63.35%;南瓜幼苗的根SOD活性、叶片SOD活性、根CAT活性、叶片CAT活性和叶片MDA含量,黄瓜幼苗的根SOD活性、根POD活性、叶片POD活性、根CAT活性、根MDA含量,油菜幼苗的根SOD活性、叶片SOD活性、根POD活性、根CAT活性、根MDA含量分别增加了9.14倍、55.87%、60.18%、1.71倍、34.22%、13.09倍、2.82倍、93.81%、2.80倍、4.11倍、8.41倍、4.13倍、45.86%、5.84倍和6.72倍。1、10 mg·L^-1镉处理南瓜幼苗的叶片POD活性分别增加了97.70%和89.84%;南瓜幼苗的根CAT活性分别降低了67.12%和53.18%。1、10、100 mg·L^-1镉处理黄瓜幼苗的叶片CAT活性分别降低了78.03%、28.10%和33.11%;南瓜幼苗的根POD活性分别增加了7.47倍、3.46倍和19.59倍;黄瓜幼苗的叶片SOD活性分别增加了87.13%、124.18%和108.46%,叶片MDA含量分别增加了98.26%、32.65%和27.26%;油菜幼苗的叶片POD活性分别增加了71.97%、117.10%和2.27倍。总之,高浓度镉抑制南瓜、黄瓜和油菜幼苗的生长发育。

Efficient scar-free knock-ins of several kilobases in plants by engineered CRISPR-Cas endonucleases

In plants and mammals,non-homologous end-joining is the dominant pathway to repair DNA doublestrand breaks,making it challenging to generate knock-in events.In this study,we identified two groups of exonucleases from the herpes virus and the bacteriophage T7 families that conferred an up to 38-fold increase in homology-directed repair frequencies when fused to Cas9/Cas12a in a tobacco mosaic virus-based transient assay in Nicotiana benthamiana.We achieved precise and scar-free insertion of several kilobases of DNA both in transient and stable transformation systems.In Arabidopsis thaliana,fusion of Cas9 to a herpes virus family exonuclease led to 10-fold higher frequencies of knock-ins in the first generation of transformants.In addition,we demonstrated stable and heritable knock-ins in wheat in 1%of the primary transformants.Taken together,our results open perspectives for the routine production of heritable knock-in and gene replacement events in plants.

A chromosome-scale genome assembly of Rauvolfia tetraphylla facilitates identification of the complete ajmaline biosynthetic pathway

Dear Editor,Rauvolfia tetraphylla(aka the Devil pepper)(Supplemental Figure 1)is a well-known medicinal plant that produces monoterpenoid indole alkaloids(MIAs).This MIA biosynthesis occurs in several organs,including leaves,stems,fruit,and roots,which accumulate the famous antiarrhythmic ajmaline(Kumar et al.2016a,2016b;Kumara et al.,2019).MIAs are natural products notably involved in plant adaptation to the environment and defense against aggressors.This mainly results from their high biological activities,which also explain their pharmacological properties.