Exposure of meiosis-to-microspore-stage tomato flowers to long-term mild heat results in pollen failure after mitosis

Crop reproductive success is significantly challenged by heatwaves, which are increasing in frequency globally. The main reason is reduced male fertility due to abnormal pollen development, but the mechanism behind the developmental deviation is not well understood. Here, long-term mild heat (LTMH) treatment, mimicking a heatwave, was applied to flowers or whole plants and followed up by cytological, transcriptomic and biochemical analyses. LTMH was shown to act directly on the flowers and not via a systemic effect on other plant tissue. The meiosis to early microspore stage was the most to LTMH and three to four days of LTMH exposure around this period was sufficient to significantly reduce pollen viability. Extensive cytological analysis showed that abnormalities in pollen development could first be observed after pollen mitosis I and tapetum development appeared unaffected. Transcriptomic and biochemical analyses suggested that pollen development suffers from tapetal ER stress, with a limited role for oxidative stress. These characteristics differentiate the response of developing anthers and pollen to LTMH from that to severe heat stress. Overall design 12 samples in total, consisting of 3 sample types with 4 replicates each. Sample types: 1) control temperature (CT), 2) 1 day long-term mild heat (1D-LTMH), 3) 4 days long-term mild heat (4D-LTMH)

The Effects of Brief Heat During Early Booting on Reproductive, Developmental, and Chlorophyll Physiological Performance in Common Wheat (Triticum aestivum L.)

Rising temperatures due to climate change threaten agricultural crop productivity. As a cool-season crop, wheat is heat-sensitive, but often exposed to high temperatures during the cultivation period. In the current study, a bread wheat panel of spring wheat genotypes, including putatively heat-tolerant Australian and CIMMYT genotypes, was exposed to a 5-day mild (34°C/28°C, day/night) or extreme (37°C/27°C) heat stress during the sensitive pollen developmental stage. Worsening effects on anther morphology were observed, as heat stress increased from mild to extreme. Even under mild heat, a significant decrease in pollen viability and number of grains per spike from primary spike was observed compared with the control (21°C/15°C), with Sunstar and two CIMMYT breeding lines performing well. A heat-specific positive correlation between the two traits indicates the important role of pollen fertility for grain setting. Interestingly, both mild and extreme heat induced development of new tillers after the heat stress, providing an alternative sink for accumulated photosynthates and significantly contributing to the final yield. Measurements of flag leaf maximum potential quantum efficiency of photosystem II (Fv/Fm) showed an initial inhibition after the heat treatment, followed by a full recovery within a few days. Despite this, model fitting using chlorophyll soil plant analysis development (SPAD) measurements showed an earlier onset or faster senescence rate under heat stress. The data presented here provide interesting entry points for further research into pollen fertility, tillering dynamics, and leaf senescence under heat. The identified heat-tolerant wheat genotypes can be used to dissect the underlying mechanisms and breed climate-resilient wheat

DataSheet_2_The wilt pathogen induces different variations of root-associated microbiomes of plant.xlsx

Root-associated compartments, including the rhizosphere, rhizoplane, and endosphere, live with diverse microbial communities which profoundly affect plant growth and health. However, a systematic understanding of the microbiome assembly across the rhizosphere, rhizoplane, and endosphere under pathogen invasion remains elusive. Using 16S high-throughput sequencing, we studied how bacterial wilt disease affected the variation and assembly of the three continuous root-associated microbiomes of tobacco. The results indicated that microorganisms were gradually filtered from the rhizosphere to the endosphere. With the pathogen invasion, the rhizosphere, rhizoplane and endosphere microbiomes selected and recruited different beneficial bacterial taxa. Some recruited bacteria were also identified as keystone members in networks (i.e., Bosea in the endosphere). The microbiomes of endosphere and rhizoplane were more sensitive to plant disease than the rhizosphere microbiome. Still, response strategies of the rhizoplane and endosphere to disease were obviously different. Microbial networks of the rhizoplane became complex in diseased samples and genes involved in sporulation formation and cell cycle were enriched. However, microbial networks of the diseased endosphere were disrupted, and functional genes related to nitrogen utilization and chemotaxis were significantly increased, indicating the importance of nitrogen resources supply of plants for the endosphere microbiome under pathogen invasion. Our results provide novel insights for understanding the different responses of the root-associated microbiomes to plant disease.</p

DataSheet_1_The wilt pathogen induces different variations of root-associated microbiomes of plant.docx

Root-associated compartments, including the rhizosphere, rhizoplane, and endosphere, live with diverse microbial communities which profoundly affect plant growth and health. However, a systematic understanding of the microbiome assembly across the rhizosphere, rhizoplane, and endosphere under pathogen invasion remains elusive. Using 16S high-throughput sequencing, we studied how bacterial wilt disease affected the variation and assembly of the three continuous root-associated microbiomes of tobacco. The results indicated that microorganisms were gradually filtered from the rhizosphere to the endosphere. With the pathogen invasion, the rhizosphere, rhizoplane and endosphere microbiomes selected and recruited different beneficial bacterial taxa. Some recruited bacteria were also identified as keystone members in networks (i.e., Bosea in the endosphere). The microbiomes of endosphere and rhizoplane were more sensitive to plant disease than the rhizosphere microbiome. Still, response strategies of the rhizoplane and endosphere to disease were obviously different. Microbial networks of the rhizoplane became complex in diseased samples and genes involved in sporulation formation and cell cycle were enriched. However, microbial networks of the diseased endosphere were disrupted, and functional genes related to nitrogen utilization and chemotaxis were significantly increased, indicating the importance of nitrogen resources supply of plants for the endosphere microbiome under pathogen invasion. Our results provide novel insights for understanding the different responses of the root-associated microbiomes to plant disease.</p

List of primers used in this study.

<p>List of primers used in this study.</p

Presence of anther deformations, pollen germination rate and pollen number of wild-type Microtom and the <i>TM6</i>–RNAi line under control and CMH30 conditions.

<p>Presence of anther deformations, pollen germination rate and pollen number of wild-type Microtom and the <i>TM6</i>–RNAi line under control and CMH30 conditions.</p

Relative expression of B- and C-class genes under control and continuous mild heat conditions (CMH32) in anthers of the tomato cultivar Red setter.

<p>A, expression of the B-class genes <i>TAP3</i>, <i>TM6</i>, <i>TPI</i> and <i>LePI</i> and the C-class genes <i>TAG1</i> and <i>TAGL1</i> in young anthers of 2–3 mm. B, gene expression in mature anthers. Values represent the mean ± SE, with the mean expression in the control condition set to 1. *, significantly different from the control treatment, P<0.05; **, P<0.01; ***, P<0.001.</p

Relative expression of pistil marker genes in anthers and pistils of Red Setter grown under control conditions and continuous mild heat (CMH32).

<p>A, B, Relative expression of the <i>SlTTS</i> (A) and <i>TAGL11</i> (B) in anthers and pistils from 2-3mm flower buds and mature flowers (grown under control conditions). C, D, relative expression of <i>SlTTS</i> (C) and <i>TAGL11</i> (D) in anthers grown under control conditions (CT) and CMH32. Values represent the mean ± SE, with the mean expression in anthers (A, B) or under control conditions (C, D) at each developmental stage set to 1. *, significantly different from anther (A, B) or the control treatment (C, D), P<0.05; **, P<0.01; ***, P<0.001.</p

Cross sections of anthers and pistils from mature flowers of the tomato cultivar Red Setter grown under control and continuous mild heat conditions.

<p>A, overview of anthers grown under control conditions (CT). Scale bar: 300 μm. B, overview of anthers and pistil from CHM32. Scale bar 300 μm. C, transmitting-tissue-like cells from an anther grown under CMH32 (close up of B) on the left, and true stylar transmitting tissue from control conditions on the right. Scale bar 20 μm. D, ovule-like deformation from an anther grown under CMH32 (scale bar 30 μm). Upper inset shows overview of CMH32 anther with ovule-like deformation (scale bar 300 μm), lower inset shows a true ovule from control conditions (scale bar 50 μm). a, anther; l, locule; ov, ovule; ovl, ovule-like structure; st, style; tt, transmitting tissue; ttl, transmitting tissue-like cells; v, vascular bundle.</p