Kram Brian W, Xu Wayne W, Carter Clay J
Department of Biology, University of Minnesota Duluth, 55812, USA.
BMC Plant Biol. 2009 Jul 15;9:92. doi: 10.1186/1471-2229-9-92.
Many flowering plants attract pollinators by offering a reward of floral nectar. Remarkably, the molecular events involved in the development of nectaries, the organs that produce nectar, as well as the synthesis and secretion of nectar itself, are poorly understood. Indeed, to date, no genes have been shown to directly affect the de novo production or quality of floral nectar. To address this gap in knowledge, the ATH1 Affymetrix GeneChip array was used to systematically investigate the Arabidopsis nectary transcriptome to identify genes and pathways potentially involved in nectar production.
In this study, we identified a large number of genes differentially expressed between secretory lateral nectaries and non-secretory median nectary tissues, as well as between mature lateral nectaries (post-anthesis) and immature lateral nectaries (pre-anthesis). Expression within nectaries was also compared to thirteen non-nectary reference tissues, from which 270 genes were identified as being significantly upregulated in nectaries. The expression patterns of 14 nectary-enriched genes were also confirmed via RT PCR. Upon looking into functional groups of upregulated genes, pathways involved in gene regulation, carbohydrate metabolism, and lipid metabolism were particularly enriched in nectaries versus reference tissues.
A large number of genes preferentially expressed in nectaries, as well as between nectary types and developmental stages, were identified. Several hypotheses relating to mechanisms of nectar production and regulation thereof are proposed, and provide a starting point for reverse genetics approaches to determine molecular mechanisms underlying nectar synthesis and secretion.
许多开花植物通过提供花蜜来吸引传粉者。然而，人们对蜜腺（产生花蜜的器官）发育以及花蜜本身的合成和分泌所涉及的分子事件了解甚少。事实上，迄今为止，尚未有基因被证明直接影响花蜜的从头产生或质量。为了填补这一知识空白，利用 ATH1 艾菲梅克斯基因芯片阵列系统地研究拟南芥蜜腺转录组，以鉴定可能参与花蜜产生的基因和途径。
在本研究中，我们鉴定出大量在分泌性侧蜜腺与非分泌性中蜜腺组织之间，以及成熟侧蜜腺（花后）与未成熟侧蜜腺（花前）之间差异表达的基因。还将蜜腺内的表达与 13 个非蜜腺参考组织进行了比较，从中鉴定出 270 个在蜜腺中显著上调的基因。14 个蜜腺富集基因的表达模式也通过 RT-PCR 得到了证实。在研究上调基因的功能组时，与参考组织相比，参与基因调控、碳水化合物代谢和脂质代谢的途径在蜜腺中特别富集。
鉴定出了大量在蜜腺中优先表达的基因，以及蜜腺类型和发育阶段之间差异表达的基因。提出了几个与花蜜产生及其调控机制相关的假说，为通过反向遗传学方法确定花蜜合成和分泌的分子机制提供了一个起点。
