Interplay of Light and ABA signaling to modulate plant development.

The exogenous light cues and the phytohormone Abscisic acid (ABA) regulate several aspects of plant growth and development. In recent years, the role of the crosstalk between the light and ABA signaling pathways in regulating different physiological processes has become increasingly evident. This includes the regulation of germination and early seedling development, control of stomatal development and conductance, growth and development of roots, buds, branches, and regulation of flowering. Light and ABA signaling cascades have various convergence points at both DNA and protein levels. The molecular crosstalk involves several light signaling factors like HY5, COP1, PIFs and BBXs that integrate with ABA signaling components like the PYL receptors and ABI5. Especially, ABI5 and PIF4 promoters serve as key "hotspots" for the integration of these two pathways. Plants acquired both light and ABA signaling pathways before they colonized land almost 500 million years ago. In this review, we discuss the recent advances in the interplay of light and ABA signaling regulating plant development and provide an overview of the evolution of these two pathways.

Regulation of chloroplast biogenesis, development, and signaling by endogenous and exogenous cues.

Chloroplasts are one of the defining features in most plants, primarily known for their unique property to carry out photosynthesis. Besides this, chloroplasts are also associated with hormone and metabolite productions. For this, biogenesis and development of chloroplast are required to be synchronized with the seedling growth to corroborate the maximum rate of photosynthesis following the emergence of seedlings. Chloroplast biogenesis and development are dependent on the signaling to and from the chloroplast, which are in turn regulated by several endogenous and exogenous cues. Light and hormones play a crucial role in chloroplast maturation and development. Chloroplast signaling involves a coordinated two-way connection between the chloroplast and nucleus, termed retrograde and anterograde signaling, respectively. Anterograde and retrograde signaling are involved in regulation at the transcriptional level and downstream modifications and are modulated by several metabolic and external cues. The communication between chloroplast and nucleus is essential for plants to develop strategies to cope with various stresses including high light or high heat. In this review, we have summarized several aspects of chloroplast development and its regulation through the interplay of various external and internal factors. We have also discussed the involvement of chloroplasts as sensors of various external environment stress factors including high light and temperature, and communicate via a series of retrograde signals to the nucleus, thus playing an essential role in plants' abiotic stress response.

Integration of light and ABA signaling pathways to combat drought stress in plants.

Drought is one of the most critical stresses, which causes an enormous reduction in crop yield. Plants develop various strategies like drought escape, drought avoidance, and drought tolerance to cope with the reduced availability of water during drought. Plants adopt several morphological and biochemical modifications to fine-tune their water-use efficiency to alleviate drought stress. ABA accumulation and signaling plays a crucial role in the response of plants towards drought. Here, we discuss how drought-induced ABA regulates the modifications in stomatal dynamics, root system architecture, and the timing of senescence to counter drought stress. These physiological responses are also regulated by light, indicating the possibility of convergence of light- and drought-induced ABA signaling pathways. In this review, we provide an overview of investigations reporting light-ABA signaling cross talk in Arabidopsis as well as other crop species. We have also tried to describe the potential role of different light components and their respective photoreceptors and downstream factors like HY5, PIFs, BBXs, and COP1 in modulating drought stress responses. Finally, we highlight the possibilities of enhancing the plant drought resilience by fine-tuning light environment or its signaling components in the future.

The multitasking abilities of MATE transporters in plants.

As sessile organisms, plants constantly monitor environmental cues and respond appropriately to modulate their growth and development. Membrane transporters act as gatekeepers of the cell regulating both the inflow of useful materials as well as exudation of harmful substances. Members of the multidrug and toxic compound extrusion (MATE) family of transporters are ubiquitously present in almost all forms of life including prokaryotes and eukaryotes. In bacteria, MATE proteins were originally characterized as efflux transporters conferring drug resistance. There are 58 MATE transporters in Arabidopsis thaliana, which are also known as DETOXIFICATION (DTX) proteins. In plants, these integral membrane proteins are involved in a diverse array of functions, encompassing secondary metabolite transport, xenobiotic detoxification, aluminium tolerance, and disease resistance. MATE proteins also regulate overall plant development by controlling phytohormone transport, tip growth processes, and senescence. While most of the functional characterizations of MATE proteins have been reported in Arabidopsis, recent reports suggest that their diverse roles extend to numerous other plant species. The wide array of functions exhibited by MATE proteins highlight their multitasking ability. In this review, we integrate information related to structure and functions of MATE transporters in plants. Since these transporters are central to mechanisms that allow plants to adapt to abiotic and biotic stresses, their study can potentially contribute to improving stress tolerance under changing climatic conditions.

The CLIP-domain serine protease homolog SPCLIP1 regulates complement recruitment to microbial surfaces in the malaria mosquito Anopheles gambiae.

The complement C3-like protein TEP1 of the mosquito Anopheles gambiae is required for defense against malaria parasites and bacteria. Two forms of TEP1 are present in the mosquito hemolymph, the full-length TEP1-F and the proteolytically processed TEP1(cut) that is part of a complex including the leucine-rich repeat proteins LRIM1 and APL1C. Here we show that the non-catalytic serine protease SPCLIP1 is a key regulator of the complement-like pathway. SPCLIP1 is required for accumulation of TEP1 on microbial surfaces, a reaction that leads to lysis of malaria parasites or triggers activation of a cascade culminating with melanization of malaria parasites and bacteria. We also demonstrate that the two forms of TEP1 have distinct roles in the complement-like pathway and provide the first evidence for a complement convertase-like cascade in insects analogous to that in vertebrates. Our findings establish that core principles of complement activation are conserved throughout the evolution of animals.

Plant microProteins: Small but powerful modulators of plant development.

MicroProteins (miPs) are small and single-domain containing proteins of less than 20 kDa. This domain allows microProteins to interact with compatible domains of evolutionary-related proteins and fine-tuning the key physiological pathways in several organisms. Since the first report of a microProtein in mice, numerous microProteins have been identified in plants by computational approaches. However, only a few candidates have been functionally characterized, primarily in Arabidopsis. The recent success of synthetic microProteins in modulating physiological activities in crops makes these proteins interesting candidates for crop engineering. Here, we comprehensively summarise the synthesis, mode of action, and functional roles of microProteins in plants. We also discuss different approaches used to identify plant microProteins. Additionally, we discuss novel approaches to design synthetic microProteins that can be used to target proteins regulating plant growth and development. We finally highlight the prospects and challenges of utilizing microProteins in future crop improvement programs.