Phloem transport of flowering signals

Seasonal variability in environmental parameters such as day length regulates many aspects of plant development. The transition from vegetative growth to flowering in Arabidopsis is regulated by seasonal changes in day length through a genetically defined molecular cascade known as the photoperiod pathway. Recent advances were made in understanding the tissues in which different components of the photoperiod pathway act to regulate floral induction. These studies highlighted the key role of the FT protein, which is produced in the leaves in response to inductive day lengths and traffics through the phloem to initiate flowering at the shoot apex. Unveiling the cellular and molecular details of this systemic signaling process will be required for a complete understanding of flowering regulation and other photoperiodic processes.     

植物成花素的研究进展

许多植物由营养生长向生殖生长的转换都是由日照长度控制的,而植物叶片可感知日长信号并诱导成花素的合成。成花素从韧皮部运输到茎顶端,使顶端分生组织基因表达发生变化进而成花。其中,FT作为成花素的主要组分,在该转换过程中处于核心地位。本文综合近年的研究,介绍成花素及其作用机理。     

FT, a mobile developmental signal in plants

Plants synchronise their flowering with the seasons to maximise reproductive fitness. While plants sense environmental conditions largely through the leaves, the developmental decision to flower occurs in the shoot apex, requiring the transmission of flowering information, sometimes over quite long distances. Interestingly, despite the enormous diversity of reproductive strategies and lifestyles of higher plants, a key component of this mobile flowering signal, or florigen, is contributed by a highly conserved gene: FLOWERING LOCUS T (FT). The FT gene encodes a small globular protein that is able to translocate from the leaves to the shoot apex through the phloem. Plants have evolved a variety of regulatory networks that control FT expression in response to diverse environmental signals, enabling flowering and other developmental responses to be seasonally timed. As well as playing a key role in flowering, recent discoveries indicate FT is also involved in other developmental processes in the plant, including dormancy and bud burst.     

AGL24 acts in concert with SOC1 and FUL during Arabidopsis floral transition

Arabidopsis plants flower in response to long days (LDs). Exposure of leaves to inductive day lengths activates expression of FLOWERING LOCUS T (FT) protein which moves to the shoot apical meristem (SAM) to induce developmental reprogramming. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and FRUITFULL (FUL) are induced by FT at the apex. We previously screened the SAM for mRNAs of genes required to promote the floral transition in response to photoperiod, and conducted detailed expression and functional analyses on several putative candidates. Here, we show that expression of AGAMOUS-LIKE 24 (AGL24) is detected at the SAM under SD conditions and increases upon exposure to LDs. Mutations in AGL24 further delay flowering of a soc1 ful double mutant, suggesting that flowering is controlled by AGL24 partly independently of SOC1 and FUL.     

水稻开花期调控的分子机理研究进展

水稻准确地感知外部环境信号,通过内部复杂的基因网络做出反应,在一年中最适合的时候开花繁殖。与长日促进长日模式植物拟南芥开花相反,短日促进短日模式植物水稻开花。通过对水稻和拟南芥的开花期调控机理的对比分析,发现水稻和拟南芥有着一些相对保守的开花期控制基因,其调控机理也是相似的。另外,水稻也有一些独特的开花期控制基因和开花途径。本文着重从光周期对水稻开花期的调控途径和作用机理角度进行了阐述,并对水稻开花期的自然变异与其育种应用、生物钟关联基因、光中断现象和临界日长现象以及开花期与产量的关系进行了总结。     

Flowering: a time for integration

Flowering time is under the control of multiple environmental cues such as photoperiod and exposure to cold temperatures (vernalization). A few regulators named integrators of flowering time signals (LEAFY, SOC1 /AGL20 and FT ) integrate inputs from the different flowering cascades and convey the resulting outcome to floral meristem identity genes at the shoot apex. Here we review the current knowledge about the expression of integrators, their mode of action, their potential target genes and the nature of their mutual interactions. We emphasize the questions that have been generated by recent progress in this field and that remain to be addressed.     

大豆开花基因GmCO和GmFT的克隆及表达

为了研究大豆光周期反应是否受开花基因CO(CONSTANS)和FT(FLOWERING LOCUS T)调控,采用同源序列法从大豆中分离了CO和FT的同源物GmCO和GmFT.GmCO和GmFT分别编码151和109个氨基酸,与水稻和拟南芥中相关蛋白的氨基酸序列同源性达到70%以上.通过RT-PCR分析GmCO和GmFT在短日照(short daylength,SD)、自然光照(natural light,NL)和长日照(long daylength,LD)处理大豆不同发育阶段叶片中的表达发现,GmCO在LD处理大豆早期发育的叶片中高丰度表达,GmFT在SD和NL处理大豆开花时期的叶片中高丰度表达.上述结果表明,GmCO和GmFT的表达与大豆开花时间及光照长度密切相关,且GmCO抑制GmFT的表达.