Early and late plastid development in response to chill stress and heat stress in wheat seedlings |
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Authors: | Sasmita?Mohanty Email author" target="_blank">Baishnab?C?TripathyEmail author |
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Institution: | (1) School of Life Sciences, Jawaharlal Nehru University, New Delhi, 110 067, India;(2) Present address: School of Biotechnology, KIIT University, Bhubaneswar, India; |
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Abstract: | Five-day-old etiolated wheat (Triticum aestivum L.) seedlings were transferred to 7°C (chill stress), 25°C (control), and 42°C (heat stress) and were kept in the dark or
light for different time periods. Plastids were isolated from the control and stressed seedlings, and their low-temperature
(77 K) fluorescence emission spectra were monitored. Most of the Protochlorophyllide (Pchlide) present in heat-stressed etiolated
seedlings were in nonphototransformable form. The phototransformable Pchlide (F657) rapidly decreased when 5-day-old etiolated
seedlings were transferred to 42°C in the dark for 24 h. A flash illumination of 0.2 s given to etiolated heat-stressed seedlings
resulted in substantial arrest of Shibata shift, while in chill-stress conditions, it was only partially affected. In high
temperature, due to disaggregation of polymeric Pchlide–Pchlide oxidoreductase (POR)–nicotinamide adenine dinucleotide phosphate
(NADPH) molecules, the conversion of nonphototransformable Pchlide to its phototransformable form is substantially delayed
resulting in impaired Shibata shift and belated development of the core antenna CP47 Photosystem II (PSII). Chill stress,
however, did not disaggregate the polymeric Pchlide–POR–NADPH molecule-suppressed Pchlide and Chl synthesis and impaired of
the assembly of PSII core antenna CP47 that emits F695 and PSI that emits F735. The decreased gene/protein expression and
reduced posttranslational import of plastidic proteins, importantly POR in temperature-stressed plants, may be responsible
for the delay in conversion of nonphototransformable to phototransformable form of Pchlide and plastid biogenesis. |
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