Biomedical subjects

Jordi Bou

Publications and source records attributed to Jordi Bou.

5 recordsLinked to original sources

PubMed2006

Long-term submergence-induced elongation in Rumex palustris requires abscisic acid-dependent biosynthesis of gibberellin1.

Rumex palustris (polygonceae) responds to complete submergence with enhanced elongation of its youngest petioles. This process requires the presence of gibberellin (GA) and is associated with an increase in the concentration of GA1 in elongating petioles. We have examined how GA biosynthesis was regulated in submerged plants. Therefore, cDNAs encoding GA-biosynthetic enzymes GA 20-oxidase and GA 3-oxidase, and the GA-deactivating enzyme GA 2-oxidase were cloned from R. palustris and the kinetics of transcription of the corresponding genes was determined during a 24 h submergence period. The submergence-induced elongation response could be separated into several phases: (1) during the first phase of 4 h, petiole elongation was insensitive to GA; (2) from 4 to 6 h onward growth was limited by GA; and (3) from 15 h onward underwater elongation was dependent, but not limited by GA. Submergence induced an increase of GA1 concentration, as well as enhanced transcript levels of RpGA3ox1. Exogenous abscisic acid repressed the transcript levels of RpGA20ox1 and RpGA3ox1 and thus inhibited the submergence-induced increase in GA1. Abscisic acid had no effect on the tissue responsiveness to GA.

Abscisic Acid↗

PubMed2006

Identification of primary target genes of phytochrome signaling. Early transcriptional control during shade avoidance responses in Arabidopsis.

The phytochrome (phy) photoreceptors modulate plant development after perception of light. Upon illumination of etiolated seedlings, phys initiate a transcriptional cascade by directly transducing light signals to the promoters of genes encoding regulators of morphogenesis. In light-grown plants, however, little is known about the transcriptional cascade modulated by phys in response to changes in light. The phy entry points in this cascade are completely unknown. We are particularly interested in the shade avoidance syndrome (SAS). Here we describe a subset of six genes whose expression is rapidly modulated by phys during both deetiolation and SAS in Arabidopsis (Arabidopsis thaliana). Using cycloheximide, we provide evidence that four of these phy rapidly regulated (PAR) genes are direct targets of phy signaling during SAS, revealing these genes as upstream components of the transcriptional cascade. Promoter-beta-glucuronidase fusions confirmed that PAR genes are photoregulated at the transcriptional level. Analysis of gene expression in light signal transduction mutants showed that COP1 and DET1 (but not DET2 or HY5) play a role in modulating PAR expression in response to shade in light-grown seedlings. Moreover, genetic analyses showed that one of the genes identified as a direct target of phy signaling was phy-interacting factor 3-like-1 (PIL1). PIL1 has previously been implicated in SAS in response to transient shade, but we show here that it also plays a key role in response to long-term shade. The action of PIL1 was particularly apparent in a phyB background, suggesting an important negative role for PIL1 under dense vegetation canopies.

Arabidopsis↗

PubMed2006

Seasonal control of tuberization in potato: conserved elements with the flowering response.

Fluctuations in day length determine the time to flower in many plants and in potato are critical to promote differentiation of tubers. Day length is perceived in the leaves and under inductive conditions these synthesize a systemic signal that is transported to the underground stolons to induce tuber development. Flowering tobacco shoots grafted into potato stocks promote tuberization in the stocks, indicating that the floral and tuber-inducing signals might be similar. We describe recent progress in the identification of the molecular mechanisms underlying day-length recognition in potato. Evidence has been obtained for a conserved function of the potato orthologs of the CONSTANS (CO) and FLOWERING LOCUS T (FT) proteins in tuberization control under short days (SDs). These observations indicate that common regulatory pathways are involved in both flowering and tuberization photoperiodic responses in plants.

Flowers↗

PubMed2002

Submergence research using Rumex palustris as a model; looking back and going forward.

Flooding is a phenomenon that destroys many crops worldwide. During evolution several plant species evolved specialized mechanisms to survive short- or long-term waterlogging and even complete submergence. One of the plant species that evolved such a mechanism is Rumex palustris. When flooded, this plant species is capable to elongate its petioles to reach the surface of the water. Thereby it restores normal gas exchange which leads to a better survival rate. Enhanced levels of ethylene, due to physical entrapment, is the key signal for the plant that its environment has changed from air to water. Subsequently, a signal transduction cascade involving at least four (classical) plant hormones, ethylene, auxin, abscisic acid, and gibberellic acid, is activated. This results in hyponastic growth of the leaves accompanied by a strongly enhanced elongation rate of the petioles enabling them to reach the surface. Other factors, among them cell wall loosening enzymes have been shown to play a role as well.

Abscisic Acid↗

PubMed2001

The Interaction of Gibberellins and Photoperiod in the Control of Potato Tuberization.

Solanum tuberosum ssp. andigena plants require a short-day (SD) photoperiod for tuber formation, a process that is also affected by gibberellins (GAs). Grafting experiments have confirmed that the photoperiod is perceived in the leaves. Tuber formation, however, usually takes place in the underground stolons. In this review, photoperiod-dependent tuberization has been divided into five chronological events: SD photoperiod perception, short-term adaptive responses to SD conditions, generation and transport of tuber-inducing signal(s), tuber formation, and long-term adaptive responses to tuber growth. Within this frame of study, the interaction of GAs and photoperiod is revised. Similar to the flowering process in Arabidopsis, we suggest the existence of two independent pathways that control tuber formation: a photoperiod-dependent pathway and a GA-dependent pathway. Nevertheless, photoperiod-dependent tuber formation requires the action of GAs at specific stages to orchestrate this complex process of development.

Journal Article↗