The roles of low temperature and light in accumulation of a 31‐kDa polypeptide in the light‐harvesting apparatus of maize leaves

Abstract

Abstract Previously, accumulation of a 31‐kDa polypeptide had been observed in the light‐harvesting apparatus of thylakoids of maize leaves exposed to 5°C and high light (Hayden et al., 1986). The accumulation and disappearance of this 31‐kDa polypeptide in thylakoids of maize leaves are examined as a function of photon flux density and temperature. The accumulation of large amounts of the polypeptide at 5°C was light‐dependent during a 6‐h chill period, with 50% of maximal accumulation occurring at a photon flux density of 60 μmol m−2 s−1.Some polypeptide accumulation did occur in leaves kept in the dark at 5°C for 6 h, i.e. ca. 18% of that accumulating at a photon flux density of 1500 μmol m−2 s−1. The temperature optimum for polypeptide accumulation was ca. 9°C with greater than 50% of maximal accumulation being achieved between 5 and 11°C. The breakdown of maximally accumulated polypeptide on returning leaves to 25°C was complete after 1 h, had a half‐time of ca. 20 min and was independent of light. Breakdown of the polypeptide was also observed when thylakoids isolated from chilled leaves were incubated at 25°C. Reductions of thylakoid incubation temperature between 13 and 5°C markedly reduced the rate of polypeptide disappearance. The accumulation of the polypeptide is discussed in relation to temperature and light effects on the rate of the polypeptide synthesis and of peptidase activities. The results are also discussed in the context of accumulation of the polypeptide in maize leaves in the field and consideration is given to the possible physiological significance.