La Rocca Nicoletta, Barbato Roberto, Bonora Angelo, Dalla Valle Luisa, De Faveri Stefania, Rascio Nicoletta
Dipartimento di Biologia, Università di Padova, Via U. Bassi 58/B, Padova I-35131, Italy.
J Photochem Photobiol B. 2004 Feb 20;73(3):159-66. doi: 10.1016/j.jphotobiol.2003.12.001.
Thylakoid membrane dismantling and Lhcb and RbcS nuclear gene expression have been analysed in leaves of wheat plants grown in high fluence rate light and deprived of photoprotective carotenoids by treatments with the two bleaching herbicides, either norflurazon or amitrole. The Lhcb transcript was not detectable in cells of norflurazon-supplied leaves, having chloroplasts totally devoid of both inner membranes and pigments. In contrast, a substantial amount of Lhcb mRNA could be found in cells of amitrole-treated leaves, whose severely damaged organelles still contained few strikingly altered and photosynthetically unfunctional thylakoids, as well as chlorophyll traces. A possible relationship between chlorophyll synthesis and Lhcb expression, with the transcript level depending on the rate of pigment production in photodamaged chloroplasts is discussed. Also the RbcS expression was linked to the chloroplast membrane photodamage. However, a detectable level of transcript was still produced in norflurazon-treated cells, despite complete thylakoid demolition. Thus, the wheat cell behaviour had to be placed between that of species, such as maize, in which the RbcS expression is broken off in these conditions, and that of species, such as pea, in which it is slightly lowered. Interestingly, the dramatically photodamaged chloroplasts still maintained the ability to synthesize proteins and this allowed SSU and LSU Rubisco subunits to be found in the organelles of both norflurazon- and amitrole-treated plants.
已对在高光通量率光照下生长且通过用两种漂白除草剂（氟草敏或杀草强）处理而缺乏光保护类胡萝卜素的小麦植株叶片中的类囊体膜解体以及Lhcb和RbcS核基因表达进行了分析。在供应氟草敏的叶片细胞中未检测到Lhcb转录本，这些细胞的叶绿体完全没有内膜和色素。相比之下，在杀草强处理的叶片细胞中可发现大量Lhcb mRNA，其严重受损的细胞器仍含有少量显著改变且光合无功能的类囊体以及叶绿素痕迹。讨论了叶绿素合成与Lhcb表达之间的可能关系，转录本水平取决于光损伤叶绿体中色素产生的速率。RbcS表达也与叶绿体膜光损伤有关。然而，尽管类囊体完全解体，但在氟草敏处理的细胞中仍产生了可检测水平的转录本。因此，小麦细胞的行为介于玉米等物种（在这些条件下RbcS表达中断）和豌豆等物种（其RbcS表达略有降低）之间。有趣的是，严重光损伤的叶绿体仍保持合成蛋白质的能力，这使得在氟草敏和杀草强处理的植物细胞器中都能发现小亚基和大亚基Rubisco。
