Accumulation of pathogenesis-related proteins in barley leaf intercellular spaces during leaf senescence

Abstract

Accumulation of the pathogenesis-related (PR) proteins localised in intercellular spaces of barley primary leaves, chlorophyll content, structure of chloroplasts, and photosynthesis were examined during natural and in vitro induced leaf senescence (cultivation of whole plants in the dark or detached leaves under nutrient deficiency). Some of PR proteins accumulated during natural senescence, but their accumulation pattern was different from those of pathogen-induced as well as during in vitro-induced senescence, which indicate different molecular bases of these processes. Photosynthetic rate and chlorophyll content indicate that natural senescence of barley primary leaves began from 15th day after sowing. In 35-d-old first leaves, the chloroplasts showed typical characteristics of senescence as significant decrease of size, greater grana, and prominent plastoglobuli. The chloroplasts contained more grana under in vitro induced senescence and they had reduced length in the dark. Correspondingly, accumulation of PR proteins was detectable on about the 15th day but the content of some PR proteins increased in later stages of senescence.