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1. Non-rolling flag leaves use an effective mechanism to reduce water loss and light-induced damage under drought stress

   https://doi.org/10.1093/aob/mcac035  

   Hura, Tomasz ; Hura, Katarzyna ; Ostrowska, Agnieszka ; Urban, Karolina ( March 2022 , Annals of Botany)

   The study reports on four different types of flag leaf rolling under soil drought in relation to the level of cell wall-bound phenolics. The flag leaf colonization by aphids, as a possible bioindicator of the accumulation of cell wall-bound phenolics, was also estimated.

   The proteins of the photosynthetic apparatus that form its core and are crucial for maintaining its stability (D1/PsbA protein), limit destructive effects of light (PsbS, a protein binding carotenoids in the antennas) and participate in efficient electron transport between photosystems II (PSII) and PSI (Rieske iron–sulfur protein of the cytochrome b6f complex) were evaluated in two types of flag leaf rolling. Additionally, biochemical and physiological reactions to drought stress in rolling and non-rolling flag leaves were compared.

   The study identified four types of genome-related types of flag leaf rolling. The biochemical basis for these differences was a different number of phenolic molecules incorporated into polycarbohydrate structures of the cell wall. In an extreme case of non-rolling dehydrated flag leaves, they were found to accumulate high amounts of cell wall-bound phenolics that limited cell water loss and protected the photosynthetic apparatus against excessive light. PSII was also additionally protected against excess light by the accumulation of photosynthetic apparatus proteins that ensured stable and efficient transport of excitation energy beyond PSII and its dissipation as far-red fluorescence and heat. Our analysis revealed a new type of flag leaf rolling brought about by an interaction between wheat and rye genomes, and resulting in biochemical specialization of flexible, rolling and rigid, non-rolling parts of the flag leaf. The study confirmed limited aphid colonization of the flag leaves with enhanced content of cell wall-bound phenolics.

   Non-rolling leaves developed effective adaptation mechanisms to reduce both water loss and photoinhibitory damage to the photosynthetic apparatus under drought stress.

    

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2. MicroRNAs meet with quantitative trait loci: Small powerful players in regulating quantitative yield traits in rice

   https://doi.org/10.1002/wrna.1556  

   Peng, Ting ; Teotia, Sachin ; Tang, Guiliang ; Zhao, Quanzhi ( June 2019 , WIREs RNA)

   MicroRNAs (miRNAs) are small noncoding RNAs which regulate various functions related to growth, development, and stress responses in plants and animals. Rice,Oryza sativa, is one of the most important food crops of the world. In rice, a number of quantitative trait loci (QTL) controlling yield‐related traits have been identified. Some of them are actually controlled by miRNAs, which control various yield‐related quantitative traits in rice. On one hand, many of these miRNAs are found to regulate more than one yield‐related traits, such as tillering, grain size, and branch number of a panicle. On the other hand, a rice yield‐related trait is usually controlled by multiple miRNAs, for example, grain size being controlled by miR156, miR167, miR396, miR397, and miR1432. In rare case, a single miRNA may specifically regulate only one yield‐related trait, such as, miR444 regulating rice tillering. In this review, we focus on the functions of miRNAs in controlling yield‐related quantitative traits in rice, including panicle grain number, grain weight/size, panicle length and branching, tiller number per plant, spikelet number, seed setting rate, and leaf inclination, and discuss how to modulate the expression of these miRNAs using modern molecular biology tools to promote grain yield.

   This article is categorized under:

   RNA in Disease and Development > RNA in Development

    

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3. Semantic Segmentation of Sorghum Using Hyperspectral Data Identifies Genetic Associations

   https://doi.org/10.34133/2020/4216373  

   Miao, Chenyong ; Pages, Alejandro ; Xu, Zheng ; Rodene, Eric ; Yang, Jinliang ; Schnable, James C. ( February 2020 , Plant Phenomics)

   This study describes the evaluation of a range of approaches to semantic segmentation of hyperspectral images of sorghum plants, classifying each pixel as either nonplant or belonging to one of the three organ types (leaf, stalk, panicle). While many current methods for segmentation focus on separating plant pixels from background, organ-specific segmentation makes it feasible to measure a wider range of plant properties. Manually scored training data for a set of hyperspectral images collected from a sorghum association population was used to train and evaluate a set of supervised classification models. Many algorithms show acceptable accuracy for this classification task. Algorithms trained on sorghum data are able to accurately classify maize leaves and stalks, but fail to accurately classify maize reproductive organs which are not directly equivalent to sorghum panicles. Trait measurements extracted from semantic segmentation of sorghum organs can be used to identify both genes known to be controlling variation in a previously measured phenotypes (e.g., panicle size and plant height) as well as identify signals for genes controlling traits not previously quantified in this population (e.g., stalk/leaf ratio). Organ level semantic segmentation provides opportunities to identify genes controlling variation in a wide range of morphological phenotypes in sorghum, maize, and other related grain crops. 

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4. Tissue- and time-dependent metabolite profiles during early grain development under normal and high night-time temperature conditions

   https://doi.org/10.1186/s12870-024-05190-6  

   Abshire, Nathan ; Hauck, Andrew_L ; Walia, Harkamal ; Obata, Toshihiro ( June 2024 , BMC Plant Biology)

   Wheat grain development in the first few days after pollination determines the number of endosperm cells that influence grain yield potential and is susceptible to various environmental conditions, including high night temperatures (HNTs). Flag leaves and seed-associated bracts (glumes, awn, palea, and lemma) provide nutrients to the developing seed. However, the specific metabolic roles of these tissues are uncertain, especially their dynamics at different developmental stages and the time in a day. Tissue- and time-dependent metabolite profiling may hint at the metabolic roles of tissues and the mechanisms of how HNTs affect daytime metabolic status in early grain development.

   The metabolite profiles of flag leaf, bract, seed (embryo and endosperm), and entire spike were analyzed at 12:00 (day) and 23:00 (night) on 2, 4, and 6 days after fertilization under control and HNT conditions. The metabolite levels in flag leaves and bracts showed day/night oscillations, while their behaviors were distinct between the tissues. Some metabolites, such as sucrose, cellobiose, and succinic acid, showed contrasting oscillations in the two photosynthetic tissues. In contrast, seed metabolite levels differed due to the days after fertilization rather than the time in a day. The seed metabolite profile altered earlier in the HNT than in the control condition, likely associated with accelerated grain development caused by HNT. HNT also disrupted the day/night oscillation of sugar accumulation in flag leaves and bracts.

   These results highlight distinct metabolic roles of flag leaves and bracts during wheat early seed development. The seed metabolite levels are related to the developmental stages. The early metabolic events in the seeds and the disruption of the day/night metabolic cycle in photosynthetic tissues may partly explain the adverse effects of HNT on grain yield.

    

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5. Using the rapid A‐C i response (RACiR) in the Li‐Cor 6400 to measure developmental gradients of photosynthetic capacity in poplar

   https://doi.org/10.1111/pce.13436  

   Lawrence, Erica H. ; Stinziano, Joseph R. ; Hanson, David T. ( October 2018 , Plant, Cell & Environment)

   The rapid A‐C_iresponse (RACiR) technique alleviates limitations of measuring photosynthetic capacity by reducing the time needed to determine the maximum carboxylation rate (V_cmax) and electron transport rate (J_max) in leaves. Photosynthetic capacity and its relationships with leaf development are important for understanding ecological and agricultural productivity; however, our current understanding is incomplete. Here, we show that RACiR can be used in previous generation gas exchange systems (i.e., the LI‐6400) and apply this method to rapidly investigate developmental gradients of photosynthetic capacity in poplar. We compared RACiR‐determined V_cmaxand J_maxas well as respiration and stomatal conductance (g_s) across four stages of leaf expansion inPopulus deltoidesand the poplar hybrid 717‐1B4 (Populus tremula × Populus alba). These physiological data were paired with leaf traits including nitrogen concentration, chlorophyll concentrations, and specific leaf area. Several traits displayed developmental trends that differed between the poplar species, demonstrating the utility of RACiR approaches to rapidly generate accurate measures of photosynthetic capacity. By using both new and old machines, we have shown how more investigators will be able to incorporate measurements of important photosynthetic traits in future studies and further our understanding of relationships between development and leaf‐level physiology.

    

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