枫香叶片变色期全长转录组测序及分析

枫香因其树形优美,入秋后叶色红艳或橙黄,极具观赏价值,是优良的景观生态树种。为了解枫香叶片变色及其次级代谢过程的遗传基础,该文以枫香5个叶片变色期叶片混合样品为材料,利用单分子实时测序技术(PacBio平台)对其进行全长转录组测序。结果表明:(1)全长转录组测序共获得41.04 Gb的高质量数据,从中鉴定出全长非嵌合序列563 180条,通过聚类和去冗余,获得27 269条高质量全长转录本。在27 269条全长转录本中预测到2 035条长链非编码RNA(lncRNA),并检测出14 892个简单重复序列(SSR)位点和1 856个转录因子。(2)基因注释结果表明,NR、GO、COG、KEGG 等8个数据库共注释了24 857条转录本,KEGG数据库共获得了124个条代谢途径,主要有核糖体、碳代谢、氨基酸生物合成等,在类黄酮和叶绿素代谢途径中分别有49和71个转录本参与。上述结果初步揭示了枫香叶片变色期转录组信息以及功能特性,为后续研究枫香叶片变色分子机制、色素代谢合成途径和调控、相关功能基因克隆以及叶色改良提供基础数据。     

Functional Analysis and RNA Sequencing Indicate the Regulatory Role of Argonaute1 in Tomato Compound Leaf Development

Regardless of whether a leaf is simple or compound, the mechanism underlying its development will give rise to a full comprehension of plant morphogenesis. The role of Argonaute1 (AGO1) in the development of simple leaves has been established, but its role in the development of compound leaves remains to be characterized. In this paper, a virus-induced gene silencing (VIGS) strategy was used to dramatically down-regulate the expression of AGO1 ortholog in tomatoes, a model plant for research into compound leaves. AGO1-silenced tomato compound leaves exhibited morphological defects of leaf adaxial-abaxial and trichome development. Analysis of global gene expression profiles indicated that the silencing of AGO1 in tomato compound leaf caused significant changes in the expression of several critical genes, including Auxin Response Factor 4 (ARF4) and Non-expressor of PR5 (NPR5), which were involved in adaxial-abaxial formation and IAA15 that was found to contribute to growth of trichomes as well as Gibberellic Acid Insensitive (GAI) which participated in hormone regulation. Collectively, these results shed light on the complicated mechanism by which AGO1 regulates compound leaf development.     

Proteomic Analysis Reveals That Developing Leaves are More Sensitive to Nitrogen Fertilizer Than Mature Leaves

The size of rice leaves is tightly controlled by environmental and genetic factors. Several functional genes control leaf growth and development by regulating cell expansion and cell cycle activity. The regulation of leaf growth, particularly the effects of environmental conditions on leaf size, is still poorly understood. We examined the environmental control of leaf size in rice (Oryza sativa) by performing a comparative proteomic analysis, which showed that exposure to high-nitrogen levels produced enlarged leaves. The enhanced leaf growth occurred mainly as a result of an increased number of cell cycles. Two proteins related to cell division, FtsZ and ERBB3 binding protein, were increased by nitrogen treatment in the developing leaves. The expression of a type-A response regulator, OsRR2, was also elevated in developing leaves. OsRR2 acts as a negative regulator of cytokinin signaling and may reduce the cytokinin content in developing leaves; a low cytokinin level is necessary for leaf development. By analyzing the proteome response to nitrogen in both developing and mature leaves, we provide deeper insight into the mechanism by which nitrogen treatment affects the phenotype.     

Effects of cytokinin production under two SAG promoters on senescence and development of tomato plants

Two promoters of senescence-associated ARABIDOPSIS genes, SAG12 and SAG13, were used in tomato plants to express IPT that catalyzes the rate-limiting step in cytokinin biosynthesis. Expression of these heterologous promoters in tomato plants was analyzed using the reporter gene beta-glucuronidase. Both promoters are expressed in tomato leaves in a manner similar to their expression in ARABIDOPSIS plants. The SAG12 promoter is very specific to senescing leaves, whereas the SAG13 promoter is expressed in mature leaves prior to the onset of visible senescence and its expression increases in senescing leaves. Expression of both promoters in tomato tissues other than leaves was very low . IPT expressed under the control of SAG12 and SAG13 promoters ( PSAG12::IPT and PSAG13::IPT, respectively) resulted in suppression of leaf senescence and advanced flowering, as well as in a slight increase in fruit weight and fruit total soluble solids (TSS). However, expression of PSAG13::IPT also led to stem thickening, short internodal distances and loss of apical dominance. In contrast to the autoregulation of PSAG12::IPT, PSAG13::IPT is expressed at higher levels in mature leaves. This difference is likely due to PSAG13::IPT exhibiting two phases of expression - a senescence-independent expression prior to the onset of senescence that is not subjected to autoregulation by cytokinin, and enhanced expression throughout senescence which is autoregualted by cytokinin. This moderate different autoregulated behavior of PSAG12::IPT and PSAG13::IPT markedly influenced plant development, emphasizing the biological effects of cytokinin in addition to senescence inhibition.