Han B, Hughes D W, Galau G A, Bewley J D, Kermode A R
Department of Biological Sciences, Simon Fraser University, Burnaby, B.C., Canada.
Planta. 1997;201(1):27-35. doi: 10.1007/BF01258677.
In Ricinus communis L. (castor bean) endosperms, two classes of Late Embryogenesis Abundant (Lea) transcripts were first detected during mid-development (at 30-35 days after pollination, DAP) and peaked at 50 DAP, just prior to the onset of desiccation. Most of the Class I mRNAs declined substantially during desiccation itself; Class II mRNAs remained abundant in the mature dry (60 DAP) seed. Following imbibition, all Lea mRNAs abundant in the mature dry seed declined rapidly (within 5-24 h). Premature drying of developing 35-DAP seeds resulted in the loss of storage-protein mRNAs (Leg B Mat I); following rehydration, mRNAs encoding post-germinative proteins (Germ D91, D30 and D38) increased in the endosperm. The Lea mRNAs present in the developing fresh seed at 35 DAP were preserved, but did not increase in response to premature desiccation; upon rehydration these Lea mRNAs declined within 5 h. During seed development, substantial changes occurred in the synthesis of a subset of LEA proteins referred to as "dehydrins'; in particular, new dehydrin polypeptides were induced between 40 and 60 DAP. Such proteins were not as evident in prematurely dried endosperms. In contrast to the rapid loss of Lea mRNAs during germination, many of the dehydrin proteins abundant in the dried seed persisted following imbibition or rehydration.
在蓖麻（Ricinus communis L.）胚乳中，两类晚期胚胎发生丰富（Lea）转录本最早在发育中期（授粉后30 - 35天，DAP）被检测到，并在授粉后50天达到峰值，恰好在脱水开始之前。大多数I类mRNA在脱水过程中大幅下降；II类mRNA在成熟干燥（授粉后60天）种子中仍大量存在。吸胀后，成熟干燥种子中所有丰富的Lea mRNA迅速下降（在5 - 24小时内）。发育到35天的种子过早干燥导致储存蛋白mRNA（Leg B Mat I）丢失；再水化后，胚乳中编码萌发后蛋白质（Germ D91、D30和D38）的mRNA增加。在35天发育新鲜种子中存在的Lea mRNA得以保留，但未因过早脱水而增加；再水化后，这些Lea mRNA在5小时内下降。在种子发育过程中，被称为“脱水素”的一类Lea蛋白的合成发生了显著变化；特别是，在授粉后40至60天诱导产生了新的脱水素多肽。这类蛋白质在过早干燥的胚乳中不那么明显。与萌发过程中Lea mRNA的快速丢失形成对比的是，干燥种子中大量存在的许多脱水素蛋白在吸胀或再水化后仍然存在。
