Jorge José Casal

University of Buenos Aires | UBA · Institute for Agricultural Plant Physiology and Ecology (IFEVA)

Canopy shade enhances the activity of PHYTOCHROME INTERACTING FACTORs (PIFs) to boost auxin synthesis in the cotyledons. Auxin, together with local PIFs and their positive regulator CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1), promotes hypocotyl growth to facilitate access to light. Whether shade alters the cellular redox status thereby affecting grow...

Abscisic acid (ABA) and gibberellic acid (GA3) are regulators of fruit color and sugar levels, and the application of these hormones is a common practice in commercial vineyards dedicated to the production of table grapes. However, the effects of exogenous ABA and GA3 on wine cultivars remain unclear. We investigated the impact of ABA and GA3 appli...

Abscisic acid (ABA) and gibberellic acid (GA3) are regulators of fruit color and sugar levels, and the application of these hormones is a common practice in commercial vineyards dedicated to the production of table grapes. However, the effects of exogenous ABA and GA3 on wine cultivars remains unclear. We investigated the impact of ABA and GA3 appl...

In the field, plants face constantly changing light conditions caused by both atmospheric effects and neighbouring vegetation. This interplay creates a complex, fluctuating light environment within plant canopies. Shade-intolerant species rely on light cues from competitors to trigger shade avoidance responses, ensuring access to light for photosyn...

Plants are exposed to temperature conditions that fluctuate over different time scales, including those inherent to global warming. In the face of these variations, plants sense temperature to adjust their functions and minimize the negative consequences. Transcriptome responses underlie changes in growth, development, and biochemistry (thermomorph...

When exposed to shade from neighbours, competitive plants modify their growth patterns to improve access to light. In dense plant stands, ranging from forests to humid grasslands and crops, shade is interrupted by sunflecks penetrating the canopy. Relatively infrequent, minute-scale interruptions can significantly contribute to the daily light inpu...

Plant growth depends on the supply of carbohydrates produced by photosynthesis. Exogenously applied sucrose promotes the growth of the hypocotyl in Arabidopsis thaliana seedlings grown under short days. Whether this effect of sucrose is stronger under the environmental conditions where the light input for photosynthesis is limiting remains unknown....

The yield of maize ( Zea mays L.) crops depends on their ability to intercept sunlight throughout the growing cycle, transform this energy into biomass and allocate it to the kernels. Abiotic stresses affect these eco‐physiological determinants, reducing crop grain yield below the potential of each environment. Here we analyse the impact of combine...

Nitrate supply is fundamental to support shoot growth and crop performance, but the associated increase in stem height exacerbates the risks of lodging and yield losses. Despite their significance for agriculture, the mechanisms involved in the promotion of stem growth by nitrate remain poorly understood. Here, we show that the elongation of the hy...

In 1998, Bill Gray and colleagues showed that warm temperatures trigger arabidopsis hypocotyl elongation in an auxin-dependent manner. This laid the foundation for a vibrant research discipline. With several active members of the 'thermomorphogenesis' community, we here reflect on 25 years of elevated ambient temperature research and look to the fu...

Twenty-five years ago, a seminal paper demonstrated that warm temperatures increase auxin levels to promote hypocotyl growth in Arabidopsis thaliana. Here we highlight recent advances in auxin-mediated thermomorphogenesis and identify unanswered questions. In the warmth, PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF7 bind the YUCCA 8 gene promote...

When exposed to changes in the light environment caused by neighbouring vegetation, shade-avoiding plants modify their growth and/or developmental patterns to access more sunlight. In Arabidopsis (Arabidopsis thaliana), neighbour cues reduce the activity of the photo-sensory receptors phytochrome B (phyB) and cryptochrome 1 (cry1), releasing photor...

When neighbouring competitors shade the tip of a leaf, differential growth at the other end of the organ elevates its position to avoid shade. A new study elucidates how waves of growth hormones communicate these distant leaf sectors.

In agricultural crops, forests and grasslands, water deficit often occurs in the presence of cues from neighbouring vegetation. However, most studies have addressed separately the mechanisms of plant growth responses to these two aspects of the environment. Here we show that transferring Arabidopsis thaliana seedlings to agar containing polyethylen...

As the summer approaches, plants experience enhanced light inputs and warm temperatures, two environmental cues with an opposite morphogenic impact. Key components of this response are PHYTOCHROME B (phyB), EARLY FLOWERING 3 (ELF3), and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1). Here, we used single and double mutant/overexpression lines to fit a math...

Plant growth depends on the supply of carbohydrates produced by photosynthesis. Exogenously applied sucrose promotes the growth of the hypocotyl in Arabidopsis thaliana seedlings grown under short days. Whether this effect of sucrose is stronger under the environmental conditions where the light input for photosynthesis is limiting remains unknown....

Under adverse conditions such as shade or elevated temperatures, cotyledon expansion is reduced and hypocotyl growth is promoted to optimize plant architecture. The mechanisms underlying the repression of cotyledon cell expansion remain unknown. Here, we report that the nuclear abundance of the BES1 transcription factor decreased in the cotyledons...

Despite the identification of temperature sensors and downstream components involved in promoting stem growth by warm temperatures, when and how previous temperatures affect current plant growth remain unclear. Here we show that hypocotyl growth in Arabidopsis thaliana during the night responds not only to the current temperature but also to preced...

Crop floret number per unit area and, to a lesser extent grain set, are the determinants of yield that are associated with the increase in sunflower oil yield at crop densities greater than the most frequently used in Argentina of 3–5.1 pl.m⁻². A better understanding of the responses of these two yield determinants to crop density and their intra-s...

As the summer approaches, plants experience enhanced light inputs and elevated temperatures, two environmental cues with an opposite morphogenic impact. How plants integrate this conflicting information throughout seasons remains unclear. Key components of the plant response to light and temperature include phytochrome B (phyB), PHYTOCROME INTERACT...

Plants may experience large diurnal temperature fluctuations. Our knowledge of the molecular mechanisms of integration of these fluctuations and the resulting growth patterns is limited. Here we show that hypocotyl growth during the night responded not only to the current temperature but also to preceding daytime temperatures, revealing a memory of...

Shade and warmth promote the growth of the stem, but the degree of mechanistic convergence and functional association between these responses is not clear. We analysed the quantitative impact of mutations and natural genetic variation on the hypocotyl growth responses of Arabidopsis thaliana to shade and warmth, the relationship between the abundan...

Identifying the physiological traits indirectly selected during the search for high yielding maize hybrids would be useful to guide further improvements. To investigate these traits we focused on the critical period of kernel formation because kernel number is the main yield component affected by breeding. We show that breeding has increased the nu...

Phytochrome B (phyB) senses the difference between darkness and light, the level of irradiance, the red/far-red ratio, and temperature. Thanks to these sensory capacities, phyB perceives whether plant organs are buried in the soil, exposed to full sunlight, in the presence of nearby vegetation, and/or under risk of heat stress. In some species, phy...

Plant fitness depends on the adequate morphological adjustment to the prevailing conditions of the environment. Therefore, plants sense environmental cues through their life cycle, including the presence of full darkness, light, or shade, the range of ambient temperatures, the direction of light and gravity vectors, and the presence of water and mi...

Plants experience temperature fluctuations during the course of the daily cycle and although stem growth responds rapidly to these changes we largely ignore whether there is a short‐term memory of previous conditions. Here we show that night temperatures affect the growth of the hypocotyl of Arabidopsis thaliana seedlings not only during the night...

Shade-avoiding plants, including Arabidopsis (Arabidopsis thaliana), display a number of growth responses, such as elongation of stem-like structures and repositioning of leaves, elicited by shade cues, including a reduction in the blue and red portions of the solar spectrum and a low red to far-red ratio. Shade also promotes phototropism of de-eti...

Significance DELLA proteins are plant-specific transcriptional regulators that act as signaling hubs at the interface between the environment and the transcriptional networks that control growth. The growth-promoting hormone gibberellin destabilizes DELLAs. Here we describe an alternative pathway to destabilize these proteins. We show that DELLAs a...

Shade-avoiding plants including Arabidopsis thaliana display a number of growth responses elicited by shade cues including elongation of stem-like structures and repositioning of leaves. Shade also promotes phototropism of de-etiolated seedlings through repression of phytochrome B (phyB) presumably to enhance capture of unfiltered sunlight. Light c...

When exposed to neighbour cues, competitive plants increase stem growth to reduce the degree of current or future shade. The aim of this work is to investigate the impact of weather conditions on the magnitude of shade‐avoidance responses in Arabidopsis thaliana. We first generated a growth rate database under controlled conditions and elaborated a...

DELLA transcriptional regulators are central components in the control of plant body form in response to the environment. This is considered to be mediated by changes in the metabolism of the hormones gibberellins (GAs), which promote the degradation of DELLAs. However, here we show that warm temperature or shade reduced the stability of a GA-insen...

Phytochrome B (phyB) is an excellent light quality and quantity sensor that can detect subtle changes in the light environment. The relative amounts of the biologically active photoreceptor (phyB Pfr) are determined by the light conditions and light independent thermal relaxation of Pfr into the inactive phyB Pr, termed thermal reversion. Little is...

The UV-A/blue photoreceptors phototropins and cryptochromes are both known to contribute to stomatal opening (∆gs) in blue light. However, their relative contributions to maintenance of gs in blue light through the whole photoperiod remains unknown. To elucidate this question, Arabidopsis phot1 phot2 and cry1 cry2 mutants (MTs) and their respective...

When exposed to neighbour signals, competitive plants increase the growth of the stem to reduce the degree of current or future shade. Plants can experience similar neighbour cues under different weather conditions and the aim of this work is to investigate the impact of daily average temperature and irradiance and thermal amplitude on the magnitud...

Due to the preeminence of reductionist approaches, understanding of plant responses to combined stresses is limited. We speculated that light‐quality signals of neighboring vegetation might increase susceptibility to heat shocks because shade reduces tissue temperature and hence the likeness of heat shocks. In contrast, plants of Arabidopsis thalia...

When exposed to warmer, nonstressful average temperatures, some plant organs grow and develop at a faster rate without affecting their final dimensions. Other plant organs show specific changes in morphology or development in a response termed thermomorphogenesis. Selected coding and noncoding RNA, chromatin features, alternative splicing variants,...

Shade intolerant plants respond to the decrease in the red (R) to far‐red light (FR) ratio (R:FR) occurring under shade by elongating stems and petioles and re‐positioning leaves, in a race to out‐compete neighbors for the sunlight resource. In some annual species, these shade‐avoidance responses (SAS) are accompanied by the early induction of flow...

• Background and Aims Phytochrome B (phyB) is a photosensory receptor important for the control of plant plasticity and resource partitioning. Whether phyB is required to optimize plant biomass accumulation in agricultural crops exposed to full sunlight is unknown. Here we investigated the impact of mutations in the genes that encode either phyB1 o...

Long days (LD) promote flowering of Arabidopsis thaliana compared to short days (SD) by activating the photoperiodic pathway. Here we show that growth under very‐SD (3 h) or darkness (on sucrose) also accelerates flowering on a biological scale, indicating that SD actively repress flowering compared to very‐SD. CONSTANS (CO) repressed flowering und...

Vegetation shade is characterised by marked decreases in the red/far-red ratio and photosynthetic irradiance. The activity of phytochrome in the field has typically been described by its photoequilibrium, defined by the photochemical properties of the pigment in combination with the spectral distribution of the light. This approach represents an ov...

Due to the preeminence of reductionist approaches, our understanding of plant responses to combined stresses is limited. We speculated that light-quality signals of neighboring vegetation might increase susceptibility to heat shocks because shade reduces tissue temperature and hence the likeness of heat shocks. In contrast, plants of Arabidopsis th...

Agricultural crops are exposed to a range of daylengths, which act as important environmental cues for the control of developmental processes such as flowering. To explore the additional effects of daylength on plant function, we investigated the transcriptome of Arabidopsis plants grown under short days (SD) and transferred to long days (LD). Comp...

Light is the most influential environmental stimulus for plant growth. In response to deficient light, plants reprogram their development to adjust their growth in search for a light source. A fine reprogramming of gene expression orchestrates this adaptive trait. Here we show that plants alter microRNA (miRNA) biogenesis in response to light trans...

Significance In agricultural crops, plants are cultivated in close proximity, exposed to mutual shading. Photosensory receptors perceive this light environment and initiate growth responses that adjust the position of plant organs within the canopy to maximize light capture. During the early hours under shade, these responses are mediated by elevat...

Sunflecks, transient patches of light that penetrate through gaps in the canopy and transiently interrupt shade, are eco-physiologically and agriculturally important sources of energy for carbon gain, but our molecular understanding of how plant organs perceive and respond to sunflecks remains limited. The UV-B photoreceptor UV RESISTANCE LOCUS 8 (...

Abortion of fertilised ovaries at the tip of the ear can generate significant yield losses in maize crops. To investigate the mechanisms involved in this process, two maize hybrids were grown in field crops at two sowing densities and under three irrigation regimes (well-watered control, drought before pollination and drought during pollination), i...

The combined information provided by light and temperature cues helps to optimise plant body architecture and physiology. Plants possess elaborate systems to sense and respond to these stimuli. Simultaneous perception of light and temperature by dual receptors such as phytochrome B and phototropin leads to immediate signalling convergence. Converse...

Auxin has emerged as a key player in the adjustment of plant morphology to the challenge imposed by variable environmental conditions. Shade-avoidance responses, including the promotion of stem and petiole growth, leaf hyponasty, and the inhibition of branching, involve an intimate connection between light and auxin signalling. Low activity of phot...

Significance Self-organization in biological systems spans from molecular to ecosystem levels. In plant populations and communities, only a primitive mode of self-organization has been described, which involves changes in demography (survival of individuals affected by the availability of resources). Here, we show that sunflower plants cultivated i...

The presence of neighboring vegetation modifies the light input perceived by photo-sensory receptors, initiating a signaling cascade that adjusts plant growth and physiology. Thousands of genes can change their expression during this process, but the structure of the transcriptional circuit is poorly understood. Here we present a meta-analysis of t...

Light and temperature patterns often correlate in natural plant growth conditions. In this review, we analyse the perception and signalling mechanisms shared by both of these environmental cues and discuss the functional implications of their convergence to control plant growth. The first point of integration is the phytochrome B (phyB) receptor, w...

Phototropism is an asymmetric growth response enabling plants to optimally position their organs. In flowering plants, the phototropin (phot) blue light receptors are essential to detect light gradients. In etiolated seedlings, the phototropic response is enhanced by the red/far-red (R/FR)-sensing phytochromes (phy) with a predominant function of p...

Combining heat and light responses Plants integrate a variety of environmental signals to regulate growth patterns. Legris et al. and Jung et al. analyzed how the quality of light is interpreted through ambient temperature to regulate transcription and growth (see the Perspective by Halliday and Davis). The phytochromes responsible for reading the...

Donald’s ideotype and empirical evidence in cereal and oilseed crops indicate high yield is associated with less competitive plants. In this study we grew 20 chickpea lines in six environments to investigate the association between yield and intra-specific competitive ability and its genetic underpinnings using Fst genome scan based on whole genome...

Shade‐avoidance responses require CONSTITUTIVE PHOTOMORPHOGENESIS 1 ( COP 1) but the mechanisms of action of COP 1 under shade have not been elucidated. Using simulated shade and control conditions, we analysed: the transcriptome and the auxin levels of cop1 and phytochrome interacting factor 1 ( pif1 ) pif3 pif4 pif5 ( pifq ) mutants; the dynamics...

Buried seedlings must grow both strongly, to push through soil to the surface, and fast, to reach the light as quickly as possible. A recent study finds that a pair of sequentially acting E3 ubiquitin ligases balances these conflicting imperatives.

Examples of genes regulated under drought stress. (a) Up-regulated genes. (b) Down-regulated genes

We characterized transcriptional responses of potato plants to multiple abiotic stresses and used this information to identify potential mechanisms through which over-expression of the stress related transcription factor CBF1 from Arabidopsis thaliana (AtCBF1) confers multiple stress tolerance. Most transcriptional changes were specific to each con...

Long days repeatedly enhance the expression of the FLOWERING LOCUS T (FT) gene during the evening and early night. This signal induces flowering, despite low FT expression the rest of the day. To investigate whether this temporal behaviour transmits information, plants of Arabidopsis thaliana were exposed to different day-night cycles, including co...

Although cooperative interactions among kin have been established in a variety of biological systems, their occurrence in plants remains controversial. Plants of A rabidopsis thaliana were grown in rows of either a single or multiple accessions. Plants recognized kin neighbours and horizontally reoriented leaf growth, a response not observed when p...

Phytochrome A (phyA) is crucial to initiate the early steps of the transition between skoto- and photomorphogenesis upon light exposure and to complete this process under far-red light (typical of dense vegetation canopies). However, under prolonged red or white light, phyA mutants are hyper-photomorphogenic in many respects. To investigate this is...

The current consensus is that plant responses to canopy shade involve the perception of low red to far-red ratios (R:FR) by phytochrome B (phyB), which leads to the direct activation of auxin synthesis genes by PHYTOCHROME INTERACTING FACTORS (PIF). In addition to its effect on R:FR, shade also reduces irradiance, but whether shade-induced drops in...

The ratio of Red to Far Red light (R:FR) is sensed by phytochromes, including phytochrome B, and serves as a signal of potential competition. Low R:FR represses Arabidopsis thaliana branching by promoting the accumulation of abscisic acid in the young buds and by enhancing auxin signaling in the main shoot. While overall plant level branching is re...

In darkness, the dicot seedlings produce an apical hook as result of differential cell division and extension at opposite sides of the hypocotyl. This hook protects the apical meristem from mechanical damage during seedling emergence from the soil. In darkness, gibberellins act via the DELLA-PIF (PHYTOCHROME INTERACTING FACTORs) pathway, and ethyle...

In darkness, the E3 ligase COSTITUTIVE PHOTOMORPHOGENESIS 1 (COP1) targets to degradation ELONGATED HYPOCOTYL 5 (HY5) and other proteins required for photomorphogenesis (Osterlund et al., 2000; Saijo et al., 2003; Seo et al., 2003). Light inactivates COP1, allowing photomorphogenesis to proceed (Lau and Deng, 2012). Pioneer studies have demonstrate...

Waterlogging imposes a severe stress to the plant and the interplay between root and aerial organs in the adjustment to this stress is poorly understood. A set of recombinant inbred line (RILs) of Lotus japonicus (Gifu B-129 × Miyakojima MG-20) was subjected to control and waterlogging conditions for 21 days, and twelve traits related to leaf physi...

In etiolated seedlings, phytochrome A (phyA) mediates very-low-fluence responses (VLFRs), which initiate de-etiolation at the interphase between the soil and above-ground environments, and high-irradiance responses (HIR), which complete de-etiolation under dense canopies and require more sustained activation with far-red light. Light-activated phyA...

Moderately warm constant ambient temperatures tend to oppose light signals in the control of plant architecture. By contrast, here we show that brief heat shocks enhance the inhibition of hypocotyl growth induced by light perceived by phytochrome B in deetiolating Arabidopsis thaliana seedlings. In darkness, daily heat shocks transiently increased...

Low Red light:Far Red light (R:FR) serves as an indicator of impending competition and has been demonstrated to suppress branch development. The regulation of Arabidopsis rosette bud outgrowth by the R:FR and the associated mechanisms were investigated at several levels. Growth under low R:FR suppressed outgrowth of the third from topmost (n-2) bud...

In Arabidopsis thaliana, light signals modulate the defences against bacteria. Here we show that light perceived by the LOV-domain-regulated two-component system (Pst-Lov) of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) modulates virulence against A. thaliana. Bioinformatic analysis and the existence of an episomal circular intermediate indi...

Shade-avoider plants typically respond to shade-light signals by increasing the rate of stem growth. CONSTITTUTIVE PHOTOMORPHOGENESIS 1 (COP1) is an E3 ligase involved in ubiquitin labelling of proteins targeted for degradation. In dark-grown seedlings, COP1 accumulates in the nucleus and light exposure causes COP1 migration to the cytosol. Here we...

Crop management decisions such as sowing density, row distance and orientation, choice of cultivar, and weed control define the architecture of the canopy, which in turn affects the light environment experienced by crop plants. Phytochromes, cryptochromes, phototropins, and the UV-B photoreceptor UVR8 are sensory photoreceptors able to perceive spe...

The dynamic light environment of vegetation canopies is perceived by phytochromes, cryptochromes, phototropins, and UV RESISTANCE LOCUS 8 (UVR8). These receptors control avoidance responses to preclude exposure to limiting or excessive light and acclimation responses to cope with conditions that cannot be avoided. The low red/far-red ratios of shad...

While the most conspicuous response to low red/far-red ratios (R:FR) of shade light perceived by phytochrome is the promotion of stem growth, additional, less obvious effects may be discovered by studying changes in the stem transcriptome. Here, we report rapid and reversible stem transcriptome responses to R:FR in tomato (Solanum lycopersicum). As...

While studying blue light-independent effects of cryptochrome 1 (cry1) photoreceptor, we observed premature opening of the hook in cry1 mutants grown in complete darkness, a phenotype that resembles the one described for the heterotrimeric G-protein α subunit (GPA1) null mutant gpa1. Both cry1 and gpa1 also showed reduced accumulation of anthocyani...

Although multiple photoreceptors converge to control common aspects of seedling de-etiolation, we are relatively ignorant of the genes acting at or downstream of their signalling convergence. To address this issue we screened for mutants under a mixture of blue plus far-red light and identified roc1-1D. The roc1-1D mutant, showing elevated expressi...

We investigated the diurnal dependence of the hypocotyl-growth responses to shade under sunlight-night cycles in Arabidopsis thaliana. Afternoon shade events promoted hypocotyl growth, while morning shade was ineffective. The lhy-D, elf3, lux, pif4 pif5, toc1, and quadruple della mutants retained the response to afternoon shade and the lack of resp...