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High temperature promotes guard cell expansion, which opens stomatal pores to facilitate leaf cooling. How the high-temperature signal is perceived and transmitted to regulate stomatal aperture is, however, unknown. Here, we used a reverse-genetics approach to understand high temperature-mediated stomatal opening in Arabidopsis (Arabidopsis thaliana). Our findings reveal that high temperature-induced guard cell movement requires components involved in blue light-mediated stomatal opening, suggesting cross talk between light and temperature signaling pathways. The molecular players involved include phototropin photoreceptors, plasma membrane H+-ATPases, and multiple members of the 14-3-3 protein family. We further show that phototropin-deficient mutants display impaired rosette evapotranspiration and leaf cooling at high temperatures. Blocking the interaction of 14-3-3 proteins with their client proteins severely impairs high temperature-induced stomatal opening but has no effect on the induction of heat-sensitive guard cell transcripts, supporting the existence of an additional intracellular high-temperature response pathway in plants.

CONTENTS: 1049 I. 1049 II. 1050 III. 1055 IV. 1057 V. 1058 1059 References 1059 SUMMARY: Terrestrial plants rely on stomata, small pores in the leaf surface, for photosynthetic gas exchange and transpiration of water. The stomata, formed by a pair of guard cells, dynamically increase and decrease their volume to control the pore size in response to environmental cues. Stresses can trigger similar or opposing movements: for example, drought induces closure of stomata, whereas many pathogens exploit stomata and cause them to open to facilitate entry into plant tissues. The latter is an active process as stomatal closure is part of the plant's immune response. Stomatal research has contributed much to clarify the signalling pathways of abiotic stress, but guard cell signalling in response to microbes is a relatively new area of research. In this article, we discuss present knowledge of stomatal regulation in response to microbes and highlight common points of convergence, and differences, compared to stomatal regulation by abiotic stresses. We also expand on the mechanisms by which pathogens manipulate these processes to promote disease, for example by delivering effectors to inhibit closure or trigger opening of stomata. The study of pathogen effectors in stomatal manipulation will aid our understanding of guard cell signalling.

Stomatal movements rely on alterations in guard cell turgor. This requires massive K ⁺ bidirectional fluxes across the plasma and tonoplast membranes. Surprisingly, given their physiological importance, the transporters mediating the energetically uphill transport of K ⁺ into the vacuole remain to be identified. Here, we report that, in Arabidopsis guard cells, the tonoplast-localized K ⁺/H ⁺ exchangers NHX1 and NHX2 are pivotal in the vacuolar accumulation of K ⁺ and that nhx1 nhx2 mutant lines are dysfunctional in stomatal regulation. Hypomorphic and complete-loss-of-function double mutants exhibited significantly impaired stomatal opening and closure responses. Disruption of K ⁺ accumulation in guard cells correlated with more acidic vacuoles and the disappearance of the highly dynamic remodelling of vacuolar structure associated with stomatal movements. Our results show that guard cell vacuolar accumulation of K ⁺ is a requirement for stomatal opening and a critical component in the overall K ⁺ homeostasis essential for stomatal closure, and suggest that vacuolar K ⁺ fluxes are also of decisive importance in the regulation of vacuolar dynamics and luminal pH that underlie stomatal movements.

This article is a Commentary on Devireddy et al. (2020), 225: 21–25.

This article is a Commentary on Nietzel et al., 221: 1649–1664.

IntroductionChild maltreatment and other traumatic events can have serious long-term physical, social and emotional effects, including a cluster of distress symptoms recognised as ‘complex trauma’. Aboriginal and Torres Strait Islander (Aboriginal) people are also affected by legacies of historical trauma and loss. Trauma responses may be triggered during the transition to parenting in the perinatal period. Conversely, becoming a parent offers a unique life-course opportunity for healing and prevention of intergenerational transmission of trauma. This paper outlines a conceptual framework and protocol for an Aboriginal-led, community-based participatory action research (action research) project which aims to co-design safe, acceptable and feasible perinatal awareness, recognition, assessment and support strategies for Aboriginal parents experiencing complex trauma.Methods and analysisThis formative research project is being conducted in three Australian jurisdictions (Northern Territory, South Australia and Victoria) with key stakeholders from all national jurisdictions. Four action research cycles incorporate mixed methods research activities including evidence reviews, parent and service provider discussion groups, development and psychometric evaluation of a recognition and assessment process and drafting proposals for pilot, implementation and evaluation. Reflection and planning stages of four action research cycles will be undertaken in four key stakeholder workshops aligned with the first four Intervention Mapping steps to prepare programme plans.Ethics and disseminationEthics and dissemination protocols are consistent with the National Health and Medical Research Council Indigenous Research Excellence criteria of engagement, benefit, transferability and capacity-building. A conceptual framework has been developed to promote the application of core values of safety, trustworthiness, empowerment, collaboration, culture, holism, compassion and reciprocity. These include related principles and accompanying reflective questions to guide research decisions.

Child maltreatment is a global health priority affecting up to half of all children worldwide, with profound and ongoing impacts on physical, social and emotional wellbeing. The perinatal period (pregnancy to two years postpartum) is critical for parents with a history of childhood maltreatment. Parents may experience 'triggering' of trauma responses during perinatal care or caring for their distressed infant. The long-lasting relational effects may impede the capacity of parents to nurture their children and lead to intergenerational cycles of trauma. Conversely, the perinatal period offers a unique life-course opportunity for parental healing and prevention of child maltreatment. This scoping review aims to map perinatal evidence regarding theories, intergenerational pathways, parents' views, interventions and measurement tools involving parents with a history of maltreatment in their own childhoods. We searched Medline, Psychinfo, Cinahl and Embase to 30/11/2016. We screened 6701 articles and included 55 studies (74 articles) involving more than 20,000 parents. Most studies were conducted in the United States (42/55) and involved mothers only (43/55). Theoretical constructs include: attachment, social learning, relational-developmental systems, family-systems and anger theories; 'hidden trauma', resilience, post-traumatic growth; and 'Child Sexual Assault Healing' and socioecological models. Observational studies illustrate sociodemographic and mental health protective and risk factors that mediate/moderate intergenerational pathways to parental and child wellbeing. Qualitative studies provide rich descriptions of parental experiences and views about healing strategies and support. We found no specific perinatal interventions for parents with childhood maltreatment histories. However, several parenting interventions included elements which address parental history, and these reported positive effects on parent wellbeing. We found twenty-two assessment tools for identifying parental childhood maltreatment history or impact. Perinatal evidence is available to inform development of strategies to support parents with a history of child maltreatment. However, there is a paucity of applied evidence and evidence involving fathers and Indigenous parents.