Molecular and genetic control of plant thermomorphogenesis

Temperature is a major factor governing the distribution and seasonal behaviour of plants. Being sessile, plants are highly responsive to small differences in temperature and adjust their growth and development accordingly. The suite of morphological and architectural changes induced by high ambient temperatures, below the heat-stress range, is collectively called thermomorphogenesis. Understanding the molecular genetic circuitries underlying thermomorphogenesis is particularly relevant in the context of climate change, as this knowledge will be key to rational breeding for thermo-tolerant crop varieties. Until recently, the fundamental mechanisms of temperature perception and signalling remained unknown. Our understanding of temperature signalling is now progressing, mainly by exploiting the model plant Arabidopsis thaliana. The transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4) has emerged as a critical player in regulating phytohormone levels and their activity. To control thermomorphogenesis, multiple regulatory circuits are in place to modulate PIF4 levels, activity and downstream mechanisms. Thermomorphogenesis is integrally governed by various light signalling pathways, the circadian clock, epigenetic mechanisms and chromatin-level regulation. In this Review, we summarize recent progress in the field and discuss how the emerging knowledge in Arabidopsis may be transferred to relevant crop systems

A semi-automatic method for measurement of seedling length

International audienceA method for measurement of seedling length is presented here. Hand-drawn images of seedlings are converted into numerical files and processed further by the computer to obtain length approximations based on intercept measurements. Error assessment is performed based on measurement replications. The numerical results obtained on examples show that the errors are rather small compared to the biological length variation of seedlings. The high speed of measurement, the simple construction of this system and its fidelity make it very attractive for the acquisition of this type of data

Gibberellin and ethylene control endoreduplication levels in the Arabidopsis thaliana hypocotyl

International audienc

Daily Changes in the Competence for Photo- and Gravitropic Response by Potato Plantlets

Competence for phototropic (PT) and gravitropic (GT) bending by potato plantlets grown in vitro manifests regular daily changes indicating possible involvement of circadian regulation. Unilateral stimulation of plantlets with blue light at dawn resulted in moderate PT response regarding both attained curvature and long lag phase. The PT response was the strongest between 8:00 and 12:00 h. Throughout the afternoon and in the evening, bending rate and maximal PT curvature declined significantly until 23:00 h. The GT response was fastest and strongest for plantlets stimulated early in the morning and late in the evening. During the rest of the day, GT competence did not change much apart from a minimum at 15:00. In conditions comprising either prolonged day or prolonged night, plantlets appeared to maintain rhythmicity of competence for PT and GT at least in the short-term. Introduction of a dark period prior to the tropic stimulation at 11:00 h when both PT and GT responses were strong resulted in the opposite effect: PT was depressed, and GT was enhanced. There was a time threshold of 60 min for the duration of the dark period so the plants can sense interruption in the daylight. Levels of relative expression of a PHOT2 gene indicate rhythmic daily changes. The PHOT2 gene was present at high levels during morning hours and late in the evening. As the mid-day and the afternoon hours approached, PHOT2 expression decreased and reached a daily minimum at 17:00 h. We believe that our data offer strong support for the conclusion that there is an involvement of circadian rhythms in control of both PT and GT.Ministry of Education and Science of The Republic of Serbia {[}173015, 173005]Erratum in: Journal of Plant Growth Regulation (2015), 34(2): 440-450; [https://doi.org/10.1007/s00344-015-9507-8

Screening of Transgenic Citrus for HLB Resistance

Transgenic citrus scion (mostly grapefruit and sweet orange) and rootstock cultivars (Carrizo and experimental complex tetraploids) were transformed with gene(s) encoding antimicrobial peptides or systemic acquired resistance (SAR) proteins. Each transgene was under control of an enhanced CaMV 35S promoter. Several genes were also under control of a phloem specific Arabidopsis SUC2 (AtSUC2) promoter.  A number of clones of each transgenic line (at least 3 replicate plants per clone) were evaluated for resistance to Huanglongbing (HLB, caused by Candidatus Liberibacter asiaticus). 650 clones, from over 180 individual transgenic lines planted in spring 2009 in a heavily HLB infected Martin County grove were tested using qPCR for infection to HLB after 30 months in field. 396 trees tested negative for the HLB bacterium. Approximately 200 clones were observed to be healthy and flushing after 40 months in the field and were again evaluated using qPCR during June 2012. We did not detect the Ca. Liberibacter asiaticus bacterium in a majority of these trees. In a separate trial in St. Lucie County, 300 clones, from over 80 individual transgenic lines planted during 2010 were evaluated in October 2012. Similar trends were observed to that seen in our Martin County site.  345 transgenic clones and controls containing the same transgene(s) were also placed in a greenhouse containing free flying HLB-infected Asian citrus psyllids (ACP) during April 2011. All trees were evaluated for infection after 12 months by qPCR, and 80% of the transgenic trees tested negative for the bacterium.  These results suggest that some of the antimicrobial peptides and SAR-inducing proteins can provide long-term resistance against HLB