Respective contribution of CML8 and CML9, two arabidopsis calmodulin-like proteins, to plant stress responses

Abstract

In their natural environment, plants have to continuously face constraints such as biotic and abiotic stresses. To achieve their life cycle, plants have to perceive and interpret the nature, but also the strength of environmental stimuli to activate appropriate physiological responses. Nowadays, it is well established that signaling pathways are crucial steps in the implementation of rapid and efficient plant responses such as genetic reprogramming. It is also reported that rapid raises in calcium (Ca 2C ) levels within plant cells participate in these early signaling steps and are essential to coordinate adaptive responses. However, to be informative, calcium increases need to be decoded and relayed by calcium-binding proteins also referred as calcium sensors to carry-out the appropriate responses. In a recent study, we showed that CML8, an Arabidopsis calcium sensor belonging to the calmodulin-like (CML) protein family, promotes plant immunity against the phytopathogenic bacteria Pseudomonas syringae pv tomato (strain DC3000). Interestingly, other CML proteins such as CML9 were also reported to contribute to plant immunity using the same pathosystem. In this addendum, we propose to discuss about the specific contribution of these 2 CMLs in stress responses. KEYWORDSArabidopsis thaliana; biotic and abiotic stress responses; calmodulin-like protein; calcium sensor; pseudomonas syringaeIt is now well documented that most of external biotic and abiotic stimuli induce a rapid increase in free calcium levels within plant cells. 1 Calcium is considered as an ubiquitous and versatile second messenger. Indeed, calcium variations are at the heart of sophisticated signaling networks, integrating information from a diverse range of developmental cues and environmental challenges that ultimately will impact gene expression and cell physiology. 2 Interestingly, these variations can harbour stimulusspecific properties 3 and according to the nature and strength of the stimuli, calcium variations display differences in frequencies, amplitudes, cellular localization and they were defined as «Ca 2C signature». 4 These Ca 2C signatures have been proven to encode a first layer of response specificity through their spatio-temporal properties. 3,5 A second layer of specificity is brought by the decoding processes requiring calcium-binding proteins also referred as calcium sensors and their downstream targets. Ca 2C sensors are characterized by the presence in their sequence of the canonical Ca 2C -binding motif called EF-hand. 6 The Arabidopsis genome encodes at least 250 EF-hand proteins, which is much higher than in mammals, arguing for higher importance of this class of proteins in plants. 7 These Ca 2C sensors are classified into 4 major groups, the calcineurin-B like, the calciumdependent kinases, the calmodulin group and a closely related group, the CalModulin-Like protein (CML) family, which is specific to plants. 8 In 2017, we reported that the ectopic CML8 expression (P35S:: cds CML8) confers to transgenic plants a ...

Calcium Signalling in Plant Biotic Interactions

“…Gain- and loss-of-function strategies were also developed on Arabidopsis CML8 and CML9 to evaluate their physiological function in plant stress responses. These two CMLs are positive regulators of plant defence against different strains of P. syringae [ 98 , 99 , 100 ]. CML9 was first described to be involved in plant responses to abiotic stress [ 101 ] and later shown to also contribute to plant immune responses [ 97 ].…”

Towards Understanding Plant Calcium Signaling through Calmodulin-Like Proteins: A Biochemical and Structural Perspective

“…These investigations have assigned relatively specific physiological roles to several CMLs ( Table 1 ). On the one hand, the identification of specific targets for some CMLs (e.g., CML8, CML18, CML19, and CML20 [ 52 , 53 , 66 , 67 , 111 ]) ( Table 1 ) suggests that they can have diverse roles in both plant development and response to stress, different from CaM, which has broad target specificity. This brings the question of which variations in structural features, and especially of the binding pocket, might define the target specificity in CMLs.…”

“…This brings the question of which variations in structural features, and especially of the binding pocket, might define the target specificity in CMLs. On the other hand, some CMLs (CML9 [ 52 , 58 , 59 , 62 ], CML24 [ 73 , 74 , 76 ], CML37 [ 81 , 82 ], CML38 [ 84 ], and CML42 [ 30 ]) have been shown to act at crucial points in various signaling pathways, perhaps by helping plants to handle diverse environmental challenges. Therefore, at least some CMLs might behave as gateways, being able to assimilate signals from biotic and abiotic stimuli, driving signaling pathways towards a desired response.…”

Stacked genetically modified soybean harboring herbicide resistance and insecticide rCry1Ac shows strong defense and redox homeostasis disturbance after glyphosate-based herbicide application

“…Previous transcriptome studies using microarray technique to investigate the metabolic impact of GBH treatment in susceptible and resistant soybean, arabidopsis and brassica showed that most affected pathways are involved with defense metabolism [15][74] [12]. In this study, the single-transgene and stacked varieties showed up regulation of calcium-related pathways, which are essential to coordinate a rapid adaptive response in several species [75] [76]. Calmodulin protein families were also altered in both single-transgene variety (two altered genes, average 2.10 log2FC) and stacked ( ve altered genes, average 3.3 log2FC) varieties.…”