AUTHOR=Yang Zhixiao , Chen Yi , Wang Yi , Xia Haiqian , Zheng Shaoqing , Xie Shengdong , Cao Yi , Liu Jiemin , Sehar Shafaque , Lin Yingchao , Guo Yushuang , Shamsi Imran Haider 

TITLE=Nitrogen metabolic rate and differential ammonia volatilization regulate resistance against opportunistic fungus Alternaria alternata in tobacco

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1003534

DOI=10.3389/fpls.2022.1003534

ISSN=1664-462X

ABSTRACT=Nutritional correlations between plants and pathogens can crucially affect disease severity. As an essential macronutrient, the availability of nitrogen (N) and the types of  N content play a fundamental part not only in energy metabolism and protein synthesis but also in pathogenesis. However, a direct connection has not been established yet between differences in the level of resistance and N metabolism. Pertinently, former studies hold ammonia (NH3) accountable for the development of diseases in tobacco (Nicotiana tabacum L.) and in some fruits after harvest. With a purpose of pinpointing the function of NH3 volatilization on Alternaria alternate (Fries) Keissl pathogenesis and its correlation with both N metabolism and resistance differences to Alternaria alternate infection in tobacco in tobacco, leaf tissue of two tobacco cultivars with susceptibility (CBH), or resistance (JYH) were analyzed apropos of ammonia compensation point, apoplastic NH4+ concentration, pH value as well as activities of key enzymes and N status. At the leaf age of 40 to 60 d, the susceptible cultivar had a significantly higher foliar apoplastic ammonium (NH4+) concentration, pH value and NH3 volatilization potential compared to the resistant one accompanied by a significant reduction in glutamine synthetase, which in particular was a primary physiological factor causing the NH3 volatilization. The NH4+ concentration in CBH was 1.44 time higher than that in JYH, and CBH had NH3 compensation points that were 7.09, 6.15 and 4.35-fold higher than those of JYH at 40, 50 and 60 d, respectively. Moreover, the glutamate dehydrogenase activity had an upward tendency related to an increased NH4+ accumulation in both leaf tissues and apoplast but not with the NH3 compensation point. Collectively, our results strongly suggest that the accumulation of NH3 volatilization, rather than NH4+ and total N, was the primary factor inducing the Alternaria alternate infection on tobacco. Meanwhile, the susceptible cultivar was characterized by a higher N re-transfer ability of NH3 volatilization, in contrast to the disease–resistant cultivar, and had a stronger capability of N assimilation and reutilization.