Nitrogen-deficiency-induced loss in photosynthesis and modulation of β-galactosidase activity during senescence of Arabidopsis leaves

• Published in: Acta physiologiae plantarum 2017-03, Vol.39 (3), p.1-8, Article 75
• Main Authors: Pandey, Jitendra Kumar, Dash, Sidhartha Kumar, Biswal, Basanti
• Format: Article
• Language: English
• Subjects: Agriculture; Biomedical and Life Sciences; Cell walls; Chlorophyll; Enzymes; Galactosidase; Homeostasis; Leaves; Life Sciences; Nitrogen; Original Article; Photosynthesis; Plant Anatomy/Development; Plant Biochemistry; Plant Genetics and Genomics; Plant Pathology; Plant Physiology; Polysaccharides; Senescence; Stresses; Sugar; β-Galactosidase
• ISSN: 0137-5881; 1861-1664
• DOI: 10.1007/s11738-017-2371-3

Senescence-induced loss in the content of chlorophyll and the rate of oxygen evolution is remarkably enhanced when the leaves of Arabidopsis thaliana experience nitrogen-deficiency stress. On the other hand, the decline in the level of total soluble sugar during senescence is very slow and nitrogen deficiency does not exhibit any further change. The relative stability in the level of the sugar in the background of severe decline of photosynthesis may suggest the contribution of sugars from other sources to sustain its homeostasis to execute and complete energy-dependent senescence process and stress response. The possible participation of cell wall polysaccharides contributing to sugar homeostasis is predicted. Senescence-induced increase in the activity of β-galactosidase (EC 3.2.1.23) and its further enhancement in senescing leaves experiencing nitrogen stress support the proposition of participation of the enzyme for breakdown of the wall polysaccharides to sugars. The loss of photosynthesis as a possible signal for enhancement in the activity of β-galactosidase has been further examined in the excised leaves incubated in Okada and Shimura (OS) nutrient medium with and without nitrogen. Nitrogen limitation experienced by excised leaves causes rapid loss in photosynthesis with concomitant increase in the activity of the enzyme extracted both from soluble and cell wall fractions. The differential activity of the enzyme from soluble and cell wall fractions during development-dependent leaf senescence and premature senescence in excised leaves induced by nitrogen deficiency appears to be complex and needs to be resolved in the future.