植物果实成熟相关基因的转录调控

本文综述了番茄和苹果的一些果实成熟相关基因启动子的结构和作用特点,以及植物果实相关基因转录调控机制的研究现状。     

利用TIGR番茄基因索引分析挖掘果实成熟相关基因

目前,互联网上提供许多关于基因及其相关信息的数据库,从这些资料库中提取的资料信息,可用于遗传,生化,分子生物学等各种形式的研究。TIGR Tomato Gene Index数据库中的信息为研究番茄果实成熟开辟了新思路。本研究通过对该数据库的分析,发现了一些在番茄果实成熟过程中差异表达的基因。并进一步通过基因芯片软件和文献挖掘的方法对这些基因进行了分析,结果发现了一些新的与果实成熟相关的基因。这对研究番茄果实成熟提供有价值的信息和思路。     

乙烯受体在果实成熟及花衰老中的研究进展

乙烯受体是乙烯信号转导网络的第一个转导元件,通过调控受体基因的表达,可以调节植物对乙烯的敏感性,以调控果实的成熟及花衰老进程的响应。随着人们对乙烯受体研究的深入,乙烯受体突变体及受体抑制剂在采后果实和切花保鲜上的应用已受到广泛关注。就近年来关于乙烯受体的相关研究进展进行综述,重点介绍了乙烯受体的分子调控机制及乙烯受体在果实成熟和花衰老中的应用,并对今后乙烯受体的研究方向作了展望,以期为进一步研究提供参考。     

番茄rin位点上的一个MADS盒基因调控果实成熟

ｒｉｎ番茄突变体的乙烯生成和果实成熟均受到抑制 ,除此之外还表现萼片增大和花序决定性丧失。尽管该突变体维持良好的乙烯敏感性 ,但果实成熟却不能被外源乙烯诱导 ,这暗示ＲＩＮ基因编码的产物同时调控依赖于和不依赖于乙烯的成熟过程。作者先前的研究已表明ｒｉｎ位点定位于番茄第 5染色体。本文报道通过定位克隆发现ｒｉｎ位点上存在两个串联的ＭＡＤＳ盒基因 ,分别定名为ＬｅＭＡＤＳ＿ＲＩＮ和ＬｅＭＡＤＳ＿ＭＣ ,前者调控果实成熟过程而后者则影响萼片先育和花序决定性。这两个基因的功能通过正义转化ｒｉｎ番茄和反义转化野生型番…     

果实成熟的分子生物学

就番茄和其它植物果实多聚半乳糖醛酸酶（PG）基因、ACC合成酶和ACC氧化酶基因等成熟相关基因的筛选、鉴定和表达及基因工程对调控果实硬度、色泽、风味等方面的应用与前景作了评述。     

CNR转录因子在番茄果实成熟过程中的功能

SPL转录因子在植物中广泛存在并参与植物生长、发育和成熟过程,CNR是SPL转录因子家族中的一个成员,其作用机制尚不清楚。通过RNA-seq、qRT-PCR和染色质免疫共沉淀技术(ChIP)确定转录因子CNR直接作用的新的靶基因,旨在揭示番茄果实成熟过程中CNR的转录调控网络。通过RNA-seq筛选出野生型AC和突变体Cnr番茄果实中有10223个差异表达基因,这些基因涉及番茄果实生长和发育的许多方面。qRT-PCR验证的结果和转录组测序数据一致,发现甘露聚糖-1,4-β-甘露糖苷酶基因、亚油酸9S-脂氧合酶基因、果胶酯酶基因、八氢番茄红素合成酶基因、1-氨基环丙烷-1-羧酸合成酶基因、乙烯响应因子基因、多聚半乳糖醛酸酶基因和果胶裂解酶基因在AC和Cnr番茄果实中的表达量有显著差异。同时,在这些基因的启动子区域发现了转录因子CNR的结合位点GTAC基序,揭示CNR可能直接调控这些基因的转录,最后通过ChIP分析进一步验证了这个假设。转录因子CNR新靶基因涉及脂代谢、细胞壁、番茄红素合成和乙烯生物合成途径,CNR通过这些途径在番茄果实成熟过程中起作用。     

果实成熟衰老过程中蛋白质组学研究进展

蛋白质组学已开始应用于果实成熟衰老研究,以明确蛋白差异表达与成熟衰老的关系和深入揭示果实成熟衰老过程的分子机制。本文综述了蛋白质组学在果实成熟衰老研究中的重要性、果实样品蛋白的提取制备方法,重点介绍了蛋白质组学在果实成熟衰老机制、果实抗病性机制、冷害机制以及采后处理对果实成熟调控研究中的应用,分析了蛋白质组学在果实成熟衰老研究中存在的不足,提出了今后研究的方向。     

番茄果实中乙烯与多聚半乳糖醛酸酶的关系

乙烯与多聚半乳糖醛酸酶(PG)都是果实成熟过程中关键的调节因子.一方面,在有乙烯合成缺陷的转反义ACS番茄和乙烯感受缺陷的Nr突变体番茄果实中PG基因表达量都明显下降,PG酶活性明显降低;用外源乙烯(100 μL/L)处理绿熟期番茄果实使PG基因的表达明显增强,而1-甲基环丙烯(1-MCP,1 μL/L)处理转色期番茄果实明显抑制PG基因表达.另一方面,转反义PG基因番茄果实乙烯释放量在授粉后低于其野生型,番茄乙烯受体基因LeETR4和乙烯反应因子LeERF2基因表达量比野生种低.PG降解果胶的产物D-GA(100 mg/L)促进未熟期番茄果实中的乙烯生成和LeETR4、LeERF2基因的表达.     

SlCBL1基因调控番茄果实成熟发育的分子机理

以番茄(Solanum lycopersicum L.)品种‘Micro Tom’为试材,从其果实中克隆得到番茄类钙调磷酸酶B基因(Tomato Calcineurin B-Like gene,SlCBL1),构建其带有报告基因的e-GFP植物表达载体,分析番茄果实中SlCBL1基因超表达与成熟发育进程的相互关系。结果显示:(1)与对照非转基因植株以及转空载植株相比,转SlCBL1基因番茄中SlCBL1基因过量表达,而且能够使番茄果实成熟期提前3~5d,表明SlCBL1基因可促进番茄果实成熟。(2)番茄果实成熟相关基因的表达量也受到不同程度调控,其中番茄成熟过程中的色素合成基因、乙烯路径基因以及果实成熟相关转录因子都受到强烈的调控,与对照相比表达量分别上调5~10倍。研究表明,SlCBL1基因能够促进番茄果实成熟,而且通过影响色素合成基因以及果实成熟相关转录因子来调控番茄果实成熟。     

果实成熟的基因工程研究

乙烯是催化果实成熟的内源植物激素。本文简要介绍用植物基因工程的手段分离和鉴定出乙烯合成和果实成熟有关的多聚半乳糖醛酸酶、ＡＣＣ氧化酶、ＡＣＣ合酶及ＡＣＣ脱氨酶的基因。并利用反意ＲＮＡ技术将它们的反意ＲＮＡ转入番茄中,得到了相应的反意转基因植株和果实,实现了在基因水平上对果实成熟的调控,开辟了植物育种的新途径。     

Energy conservation and dissipation in mitochondria isolated from developing tomato fruit of ethylene-defective mutants failing normal ripening: the effect of ethephon,a chemical precursor of ethylene

Alternative oxidase (AOX) and uncoupling protein (UCP) are present simultaneously in tomato fruit mitochondria. In a previous work, it has been shown that protein expression and activity of these two energy-dissipating systems exhibit large variations during tomato fruit development and ripening on the vine. It has been suggested that AOX and UCP could be responsible for the respiration increase at the end of ripening and that the cytochrome pathway could be implicated in the climacteric respiratory burst before the onset of ripening. In this study, the use of tomato mutants that fail normal ripening because of deficiencies in ethylene perception or production as well as the treatment of one selected mutant with a chemical precursor of ethylene have revealed that the bioenergetics of tomato fruit development and ripening is under the control of this plant hormone. Indeed, the evolution pattern of bioenergetic features changes with the type of mutation and with the introduction of ethylene into an ethylene-synthesis-deficient tomato fruit mutant during its induced ripening.     

The never ripe mutation blocks ethylene perception in tomato.

Seedlings of tomato fruit ripening mutants were screened for their ability to respond to ethylene. Ethylene induced the triple response in etiolated hypocotyls of all tomato ripening mutants tested except for one, Never ripe (Nr). Our results indicated that the lack of ripening in this mutant is caused by ethylene insensitivity. Segregation analysis indicated that Nr-associated ethylene insensitivity is a single codominant trait and is pleiotropic, blocking senescence and abscission of flowers and the epinastic response of petioles. In normal tomato flowers, petal abscission and senescence occur 4 to 5 days after the flower opens and precede fruit expansion. If fertilization does not occur, pedicel abscission occurs 5 to 8 days after petal senescence. If unfertilized, Nr flowers remained attached to the plant indefinitely, and petals remained viable and turgid more than four times longer than their normal counterparts. Fruit development in Nr plants was not preceded by petal senescence; petals and anthers remained attached until they were physically displaced by the expanding ovary. Analysis of engineered 1-aminocyclopropane-1-carboxylate (ACC) synthase-overexpressing plants indicated that they are phenotypic opposites of Nr plants. Constitutive expression of ACC synthase in tomato plants resulted in high rates of ethylene production by many tissues of the plant and induced petiole epinasty and premature senescence and abscission of flowers, usually before anthesis. There were no obvious effects on senescence in leaves of ACC synthase overexpressers, suggesting that although ethylene may be important, it is not sufficient to cause tomato leaf senescence; other signals are clearly involved.     

Ethylene insensitivity conferred by the Green-ripe and Never-ripe 2 ripening mutants of tomato

The ripening of a fleshy fruit represents the summation of an array of biochemical processes that are regulated by interactions between developmental programs and environmental inputs. Analysis of tomato (Solanum lycopersicum) mutants and inhibitor studies indicate that ethylene is necessary for full development of the ripening program of climacteric fruit such as tomato, yet ethylene alone is not sufficient. This suggests that an interaction between ethylene and nonethylene (or developmental) pathways mediates ripening. In this study, we have examined the physiological basis for ripening inhibition of the dominant Green-ripe (Gr) and Never-ripe 2 (Nr-2) mutants of tomato. Our data suggest that this inhibition is due to ethylene insensitivity in mutant fruit. Further investigation of ethylene responses in Gr and Nr-2 plants also revealed weak ethylene insensitivity during floral senescence and abscission and, during inhibition of root elongation, a phenotype associated with the triple response. However, ethylene-induced inhibition of hypocotyl elongation and petiole epinasty are normal in Gr and Nr-2, suggesting that these loci regulate a subset of ethylene responses. We have mapped both dominant mutations to a 2-cM overlapping region of the long arm of chromosome 1 of tomato, a region not previously linked to any known ethylene signaling loci. The phenotypic similarity and overlapping map location of these mutations suggest Gr and Nr-2 may be allelic and may possibly encode a novel component of the ethylene response pathway.     

cDNA cloning and characterisation of novel ripening-related mRNAs with altered patterns of accumulation in the ripening inhibitor (rin) tomato ripening mutant

A cDNA library produced from mRNA isolated from the pericarp of wild-type tomato fruit (Lycopersicon esculentum Mill. cv Ailsa Craig) at the first visible sign of fruit ripening was differentially screened to identify clones whose homologous mRNAs were present at reduced levels in fruit of the tomato ripening mutant, ripening inhibitor,rin. Five clones were isolated (pERT 1, 10, 13, 14, 15). Accumulation of mRNA homologous to each of these clones increased during the ripening of wild-type fruit and showed reduced accumulation in ripening rin fruit. The levels of three of them (homologous to ERT 1, 13 and 14) were increased by ethylene treatment of the mutant fruit. A further clone, ERT 16 was identified for a mRNA present at a high level in both normal and mutant fruit at early stages of ripening. Database searches revealed no significant homology to the DNA sequence of ERT 14 and 15; however, DNA and derived amino acid sequence of ERT 1 both contain regions of homology with several reported UDP-glucosyl and glucuronosyl transferases (UDPGT) and with a conserved UDPGT motif. A derived amino acid sequence from the ERT 10 cDNA contains a perfect match to a consensus sequence present in a number of dehydrogenases. The ERT 13 DNA sequence has homology with an mRNA present during potato tuberisation. The presence of these mRNAs in tomato fruit is unreported and their role in ripening is unknown. The ERT 16 DNA sequence has homology with a ripening/stress-related cDNA isolated from tomato fruit pericarp.     

SPINDLY interacts with EIN2 to facilitate ethylene signalling-mediated fruit ripening in tomato

The post-translational modification of proteins enables cells to respond promptly to dynamic stimuli by controlling protein functions. In higher plants, SPINDLY (SPY) and SECRET AGENT (SEC) are two prominent O-glycosylation enzymes that have both unique and overlapping roles; however, the effects of their O-glycosylation on fruit ripening and the underlying mechanisms remain largely unknown. Here we report that SlSPY affects tomato fruit ripening. Using slspy mutants and two SlSPY-OE lines, we provide biological evidence for the positive role of SlSPY in fruit ripening. We demonstrate that SlSPY regulates fruit ripening by changing the ethylene response in tomato. To further investigate the underlying mechanism, we identify a central regulator of ethylene signalling ETHYLENE INSENSITIVE 2 (EIN2) as a SlSPY interacting protein. SlSPY promotes the stability and nuclear accumulation of SlEIN2. Mass spectrometry analysis further identified that SlEIN2 has two potential sites Ser771 and Thr821 of O-glycans modifications. Further study shows that SlEIN2 is essential for SlSPY in regulating fruit ripening in tomatoes. Collectively, our findings reveal a novel regulatory function of SlSPY in fruit and provide novel insights into the role of the SlSPY-SlEIN2 module in tomato fruit ripening.     

Altered chloroplast development and delayed fruit ripening caused by mutations in a zinc metalloprotease at the lutescent2 locus of tomato

The chloroplast is the site of photosynthesis in higher plants but also functions as the center of synthesis for primary and specialized metabolites including amino acids, fatty acids, starch, and diverse isoprenoids. Mutants that disrupt aspects of chloroplast function represent valuable tools for defining structural and biochemical regulation of the chloroplast and its interplay with whole-plant structure and function. The lutescent1 (l1) and l2 mutants of tomato (Solanum lycopersicum) possess a range of chlorophyll-deficient phenotypes including reduced rates of chlorophyll synthesis during deetiolation and enhanced rates of chlorophyll loss in leaves and fruits as they age, particularly in response to high-light stress and darkness. In addition, the onset of fruit ripening is delayed in lutescent mutants by approximately 1 week although once ripening is initiated they ripen at a normal rate and accumulation of carotenoids is not impaired. The l2 locus was mapped to the long arm of chromosome 10 and positional cloning revealed the existence of a premature stop codon in a chloroplast-targeted zinc metalloprotease of the M50 family that is homologous to the Arabidopsis (Arabidopsis thaliana) gene ETHYLENE-DEPENDENT GRAVITROPISM DEFICIENT AND YELLOW-GREEN1. Screening of tomato germplasm identified two additional l2 mutant alleles. This study suggests a role for the chloroplast in mediating the onset of fruit ripening in tomato and indicates that chromoplast development in fruit does not depend on functional chloroplasts.