Bruno Arianna K, Wetzel Carolyn M
Department of Biology, Smith College, Northampton, MA 01063, USA.
J Exp Bot. 2004 Dec;55(408):2541-8. doi: 10.1093/jxb/erh273. Epub 2004 Oct 8.
Chloroplast-to-chromoplast transitions during fruit ripening require massive transformation of the plastid internal membrane structure as the photosynthetic apparatus is disassembled. Early Light-Inducible Proteins (ELIPs) are known to accumulate in chloroplasts during thylakoid biogenesis and under stressful conditions. To determine if ELIP may also play a role in thylakoid disassembly during the chloroplast-to-chromoplast transition, ELIP mRNA expression was measured in tomato, Lycopersicon esculentum Mill. cv. Rutgers. An EST clone was identified in the Tomato Genome Project/Solanaceae Genomics Network database that has high sequence similarity with the amino acid sequence of Arabidopsis ELIP1 and ELIP2. It has complete identity in the two conserved regions of the protein. Genomic Southern blots indicate that the gene is a single copy in tomato. The genomic sequence shows the three-exon structure typical of ELIP sequences from other species. mRNA for this gene is barely detectable on northern blots from etiolated seedlings, but transiently accumulates to high levels 2 h after transfer to the light. Greenhouse-grown tomatoes were used to measure ELIP mRNA accumulation during fruit development and ripening. Tomato ELIP mRNA is detectable in all stages of fruit ripening, but is most abundant in the breaker/turning stage of development. A survey of tomato EST databases revealed that ELIP cDNA is also relatively abundant in developing flowers, which contain yellow chromoplasts. Combined, these results suggest that ELIP may play a newly-recognized role in the chloroplast-to-chromoplast transition process.
果实成熟过程中叶绿体向有色体的转变需要随着光合机构的解体对质体内膜结构进行大规模改造。已知早期光诱导蛋白（ELIPs）在类囊体生物合成过程中以及在胁迫条件下会在叶绿体中积累。为了确定ELIP是否也可能在叶绿体向有色体转变过程中的类囊体解体中发挥作用，在番茄（Lycopersicon esculentum Mill. cv. Rutgers）中测量了ELIP mRNA的表达。在番茄基因组计划/茄科基因组网络数据库中鉴定出一个EST克隆，它与拟南芥ELIP1和ELIP2的氨基酸序列具有高度的序列相似性。该蛋白在两个保守区域具有完全相同的序列。基因组Southern杂交表明该基因在番茄中是单拷贝的。基因组序列显示出其他物种ELIP序列典型的三外显子结构。在黄化苗的Northern杂交中几乎检测不到该基因的mRNA，但在转移到光照后2小时会短暂积累到高水平。使用温室种植的番茄来测量果实发育和成熟过程中ELIP mRNA的积累。番茄ELIP mRNA在果实成熟的所有阶段都可检测到，但在发育的破色/转色阶段最为丰富。对番茄EST数据库的一项调查显示，ELIP cDNA在发育中的花中也相对丰富，这些花含有黄色有色体。综合这些结果表明，ELIP可能在叶绿体向有色体的转变过程中发挥新认识到的作用。
