MicroRNAs and Their Exploration for Developing Heavy Metal-tolerant PlantsJamla, Monica; Patil, Suraj; Joshi, Shrushti; Khare, Tushar; Kumar, Vinay
doi: 10.1007/s00344-021-10476-2pmid: N/A
Heavy metals (HMs), in particular the toxic/carcinogenic non-essential ones including cadmium (Cd), arsenic (As), aluminum (Al), mercury (Hg), and lead (Pb) are known to exert severe impacts on plant growth and yields. HM contamination and/or toxicity is seen a major threat for global food production, quality, and security. Plants use intricate molecular mechanisms for responding and adapting to HM stress, both at transcriptional and post-transcriptional levels, and microRNA (miRNA) have emerged as key post-transcriptional regulators. These tiny (19–25 nucleotide) non-coding RNA species found abundantly in plants are pivotal in tight regulation of gene expression via miRNA-directed mRNA cleavage, translational repression, chromatin remodeling, or through epigenetic modification. MiRNAs are reported to be involved in regulation of HM uptake and transport, besides their chelation and homeostasis, as well as in HM-induced oxidative stress and antioxidative defense. There are also reports of involvement of miRNAs in metallic cross- and co-tolerance. Technological advents in small RNA sequencing coupled with computational tools and databases have resulted into the identification, characterization, and validation of several HM-responsive miRNAs along with their respective target genes. Through his review, we present and discuss current understandings on miRNAs, their biosynthesis, and functions in plants, emphasizing on HM stress responses and adaptations. The main aim of this review is to discuss the possible exploration of plant miRNAs as potential targets for engineering plants (via loss-/gain-of-function approaches) to confer HM tolerance. Successful case studies, current challenges, and future directions are also discussed.
Comparative Transcriptome Analysis Reveals Potential Gene Modules Associated with Cold Tolerance in Sugarcane (Saccharum officinarum L.)Huang, Xing; Liang, Yongsheng; Zhang, Baoqing; Song, Xiupeng; Li, Yangrui; Li, Changning; Qin, Zhengqiang; Li, Dewei; Wei, Jiguang; Wu, Jianming
doi: 10.1007/s00344-021-10437-9pmid: N/A
Sugarcane is an important crop worldwide, and most sugar is derived directly from sugarcane. Due to its thermophilic nature, the yield of sugarcane is largely influenced by extreme climate conditions, especially cold stress. Therefore, the development of sugarcane with improved cold tolerance is an important goal. However, little is known about the multiple mechanisms underlying cold acclimation at the bud stage in sugarcane. In this study, we emphasized that sensitivity to cold stress was higher for the sugarcane variety ROC22 than for GT42, as determined by physical signs, including bud growth capacity, relative conductivity, malonaldehyde contents, and soluble sugar contents. To understand the factors contributing to the difference in cold tolerance between ROC22 and GT42, comparative transcriptome analyses were performed. We found that genes involved in the regulation of the stability of the membrane system were the relative determinants of difference in cold tolerance. Additionally, genes related to protein kinase activity, starch metabolism, and calcium signal transduction were associated with cold tolerance. Finally, 25 candidate genes, including 23 variety-specific and 2 common genes, and 7 transcription factors were screened out for understanding the possible cold resistance mechanism. The findings of this study provide candidate gene resources for cold resistance and will improve our understanding of the regulation of cold tolerance at the bud stage in sugarcane.
Effects of Uniconazole on Leaves Photosynthesis, Root Distribution and Yield of Mung Bean (Vigna radiata)Zhou, Hang; Zheng, Dianfeng; Feng, Naijie; Shen, Xuefeng
doi: 10.1007/s00344-021-10455-7pmid: N/A
Uniconazole was a plant growth retardant with effect of regulating plant growth and development, however, there were very few studies on its application to mung bean. In this study, the leaves of mung bean were sprayed with uniconazole solution (30 mg·L−1) at V3 stage. Photosynthetic indicators, root distribution were measured at R5 and R6, and yield and components were measured at maturity. Uniconazole increased Gs (stomatal conductance) and Tr (transpiration rate) at R5 and R6, Pn (net photosynthesis rate) at R6, and SPAD value at R5. The SPAD value at R5 had the greatest correlation with yield with a correlation coefficient of 0.684. According to distribution pattern of decreasing root length density from top to bottom, large amounts of water absorbed by the roots was more likely to come from the upper soil layer, especially 0–20 cm soil layer. As the depth of soil layer increased, the proportion of root dry weight in different soil layers were 69, 14, 9, 5 and 3%, respectively. Uniconazole effectively reduced root proportion in 0–20 cm soil layer and increased root proportion in 20–60 cm soil layer. Root dry weight density in 20–40 cm soil layer and yield were significantly positively correlated (r = 0.938* at R5, r = 0.891* at R6). In addition, uniconazole increased hundred grain weight and yield, reduced pods number per plant and seeds number per pod. Based on the results, this study can provide guidance for mung bean production and high-yield breeding in the future.
Physiological Mechanism of Drought-Resistant Rice Coping With Drought StressWang, Benfu; Yang, Xiaolong; Chen, Liang; Jiang, Yuanyuan; Bu, Hongying; Jiang, Yang; Li, Ping; Cao, Cougui
doi: 10.1007/s00344-021-10456-6pmid: N/A
Drought stress is one of the major threats to rice production. The weakening of leaf photosynthesis due to drought is the main reason for the reduction of grain yield, but its mechanism is still obscure. The objectives of this study were to reveal the physiological mechanism of drought stress affecting photosynthetic capacity and grain yield. Pot experiments were conducted with drought-tolerant cultivars Hanyou113 (HY113) and Zhonghan3 (ZH3) and drought-sensitive cultivar Huanghuazhan (HHZ) under four water management treatments (traditional flooding (CK), mild drought stress (LD), moderate drought stress (MD) and severe drought stress (HD)) at heading stage in 2013 and 2014. Compared with CK, grain yield was significantly reduced by 14.9%, 30.8%, and 12.8% in HY113, HHZ, and ZH3 under LD, 32.9%, 33.7%, and 22.9% in HY113, HHZ and ZH3 under MD and 53.6%, 45.6%, and 30.7% in HY113, HHZ, and ZH3 under HD, respectively. The photosynthetic rate (Pn) decreased by 49.0% from 20.0 to 10.2 µmol m−2 s−1 in HY113, and 67.6% from 23.4 to 7.58 µmol m−2 s−1 in HHZ, and 39.3% from 23.4 to 14.2 µmol m−2 s−1 in ZH3 under HD. The Pn of HHZ was similar to that of ZH3 under CK conditions. During the drought periods from LD to HD at heading stage, the leaf water potential (LWP) reduced 31.9%, 54.8%, and 15.7% in HY113, HHZ, and ZH3, respectively. The non-photochemical quenching (NPQ) of HY113, HHZ, and ZH3 flag leaves increased by 150%, 97.6%, and 218%, respectively. The effective quantum yield of PSII photochemistry (ΦPSII) of flag leaves reduced by 20.3%, 11.9%, and 22.1% in HY113, HHZ, and ZH3, respectively. The enzymatic activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased by 11.4%, 18.0%, and 21.8% in HY113, and 13.2%, 14.3%, and 30.9% in HHZ, and 13.4% 21.7%, and 17.6% in ZH3 under MD on average across two seasons. The yield reduction of drought-resistant cultivars (HY113, ZH3) was smaller than that of conventional cultivars (HHZ). Maintaining leaf water potential (LWP), Pn, photosystem II (PSII) original light energy conversion efficiency, non–photochemical quenching coefficient (NPQ), and increasing in the ratio of photochemical reaction energy in fluorescence and antioxidant enzyme activity is the physiological basis to achieve a relatively high photosynthesis. These traits could be the target for breeder to develop drought-tolerant varieties.
The Interactive Effect of Selenium and Farmyard Manure on Soil Microbial Activities, Yield and Selenium Accumulation by Wheat (Triticum aestivum L.) GrainsKhalid, Muhammad Usman; Imran, Muhammad; Aslam, Muhammad; Ashraf, Muhammad
doi: 10.1007/s00344-021-10465-5pmid: N/A
This study assessed the interactive effect of selenium (Se) and farmyard manure (FYM) on soil microbial activities, growth, yield, and Se accumulation by wheat grains. Preliminarily, the effect of Se (0–250 µg kg−1 soil) and FYM (0–12.5 g kg−1 soil) was assessed on soil microflora. Selenium exhibited an adverse impact on soil microflora; respiration was decreased at ≥ 10 µg kg−1 soil while dehydrogenase and urease activities were decreased at ≥ 125 µg kg−1 soil. At 250 µg Se kg−1 soil, respiration, dehydrogenase and urease activities were decreased by 81, 40 and 35%, respectively, on unamended soil, and by 9, 47 and 22%, respectively, on FYM-amended soil. The subsequent plant experiments were conducted with same Se and FYM rates; one was harvested 42 days after sowing and other at crop maturity. The application of 125 µg Se kg−1 and 12.5 g FYM kg−1 soil improved seedling biomass by 12.6 and 22%, respectively, while their combined use lacked synergistic effect. Similarly, at maturity Se and FYM increased grain yield while their combined effect was not synergistic. The Se-induced suppression in microbial activities was not related to yield which was improved (11% at the highest rate in unamended soil) by Se application. Selenium application increased grain Se content in a rate-dependent manner, it increased from 0 to 1025 µg kg−1 by applying 250 µg Se kg−1 soil. Moreover, FYM application decreased Se accumulation in grains. It is concluded that FYM application increased soil microbial activities and yield but reduced grain Se accumulation in wheat on Se-applied soil.
Trichoderma Synthesizes Cytokinins and Alters Cytokinin Dynamics of Inoculated Arabidopsis SeedlingsBean, Kimberly Molina; Kisiala, Anna B.; Morrison, Erin N.; Emery, R. J. Neil
doi: 10.1007/s00344-021-10466-4pmid: N/A
Trichoderma is an important genus of symbiotic fungi, commonly used around the world as biocontrol agents and as biofertilizer. Although their beneficial effects are well known and are successfully exploited in sustainable agriculture practices, the biochemical mechanisms of plant growth-promoting actions of Trichoderma and their anti-pathogen characteristics are not well understood. This study biochemically surveyed 22 strains of Trichoderma and shows that Trichoderma produces cytokinins (CKs), which has not been reported to date. The phytohormone profiles ranged from 5.34 to 379.99 pmol CKs released to 10 mL of the growth medium and comprised riboside and nucleotide derivatives of cis-zeatin (cZ) and isopentenyladenine (iP), suggesting that fungal CKs originate from a tRNA degradation pathway. We reveal a connection between the levels of free base cZ produced by Trichoderma and the inhibition rate against the pathogen Fusarium graminearum among the tested strains. Furthermore, we analyzed CK profiles of Arabidopsis plants cultured in vitro in the presence of Trichoderma strains. The inoculated plants showed increased levels of cZ-type (cZR, cZROG) and iP-type (iP, iPR) CKs—the forms which dominated CK profiles of all the fungal in vitro cultures tested in this study. The increase in the levels of cZ derivatives was accompanied by a significant reduction in plant trans-zeatin (tZ)-type CKs (tZR, tZNT, tZOG, tZ7G, tZ9G) in Arabidopsis when co-cultured with the fungus. Our work suggests that CKs produced by plant symbiotic Trichoderma strains can be used for plant growth stimulation, may impact the colonization strategy of symbiotic fungi, and include alterations to the host plant phytohormones for enhanced plant resistance against pathogens.
Examination of the M20D Auxin Conjugate Peptidase Family from Hornwort and Implications on the Evolution of the TracheophytesMedina, Edgar A.; Desind, Samuel; Hallak, Abdulkader; Alhaddad, Abdullah; Smalley, John V.; Campanella, James J.
doi: 10.1007/s00344-021-10467-3pmid: N/A
We have identified and cloned five auxin conjugate amidohydrolases (M20D peptidases) in four different hornwort species (Phaeoceros carolinianus, Megaceros tosanus, Megaceros vincentianus, and Paraphymatoceros hallii). Sequence analysis suggests that all five enzymes have greater than 60% overall similarity to tracheophyte amidohydrolases. Phylogenetic analysis supports the hypothesis that the bryophyte and tracheophyte hydrolases are derived from a common ancestor. Enzyme studies of hornwort auxin amidohydrolases all demonstrate greater activity and substrate recognition than the more ancient liverwort hydrolase (MpILR1). The mean wild-type hornwort hydrolytic activity (23.2 ± 6.8 pmol auxin released/min/ml), although higher than the liverwort activity (1.3 ± 1.1 pmol auxin released/min/ml), was almost a magnitude lower than the average activity in tracheophyte hydrolases (186.2 ± 52.1 pmol auxin released/min/ml). Two hornwort orthologues from M. vincentianus and M. tosanus possess a Glycine238/240 replacing the tracheophytically conserved Serine209, while two from P. hallii and P. carolinianus have an Alanine238 at that homologous residue location. Further enzymatic studies and three-dimensional structural analyses of the hornwort enzymes present supporting evidence that the Ala238-line of hornworts is the likely clade from which tracheophytes arose.