Adaptation of plantations to drought events in arid and semi-arid regions: Evidence from tree resilience

Analyzing the transcriptome of maize leaves under drought stress and rewatering conditions revealed that transcription factors were involved in this process, among which ZmbZIP33 of the ABSCISIC ACID-INSENSITIVE 5-like protein 5 family was induced to significantly up-regulated. The functional mechanism of ZmbZIP33 in Abscisic acd (ABA) signaling pathway and its response to drought stress and rewatering has not been studied yet. The present study found that ZmbZIP33 contains a DNA-binding and dimerization domain, has transcriptional activation activity, and is highly homologous to SbABI1,SitbZIP68 and OsABA1. The expression of ZmbZIP33 is strongly up-regulated by drought, high salt, high temperature, and ABA treatments. Overexpression of ZmbZIP33 remarkably increased chlorophyll content and root length after drought stress and rewatering, and, moreover, cause an accumulation of ABA content, thereby improving drought resistance and recovery ability in Arabidopsis. However, silencing the expression of ZmbZIP33 (BMV-ZmbZIP33) remarkably decreased chlorophyll content, ABA content, superoxide dismutase and peroxidase activities, and increased stomatal opening and water loss rate compared with BMV (control). It showed that silencing ZmbZIP33 lead to reduced drought resistance and recovery ability of maize. ABA sensitivity analysis found that 0.5 and 1 μmol/L treatments severely inhibited the root development of overexpression ZmbZIP33 transgenic Arabidopsis. However, the root growth of BMV was greatly inhibited for 1 and 5μmol/L ABA treatments, but not for BMV-ZmbZIP33. Subcellular localization, yeast two-hybrid and BIFC further confirmed that the core components of ABA signaling pathways ZmPYL10 and ZmPP2C7 interacted in nucleus, ZmPP2C7 and ZmSRK2E as well as ZmSRK2E and ZmbZIP33 interacted in the plasma membrane. We also found that expression levels of ZmPYL10 and ZmSRK2E in the BMV-ZmbZIP33 mutant were lower than those of BMV, while ZmPP2C7 was the opposite under drought stress and rewatering. However, expression of ZmPYL10 and ZmSRK2E in normal maize leaves were significantly up-regulated by 3–4 folds after drought and ABA treatments for 24 h, while ZmPP2C7 was down-regulated. The NCED and ZEP encoding key enzymes in ABA biosynthesis are up-regulated in overexpression ZmbZIP33 transgenic line under drought stress and rewatering conditions, but down-regulated in BMV-ZmbZIP33 mutants. Together, these findings demonstrate that ZmbZIP33 played roles in ABA biosynthesis and regulation of drought response and rewatering in Arabidopsis and maize thought an ABA-dependent signaling pathway.

Species mixing enhances the resistance of Robinia pseudoacacia L. to drought events in semi-arid regions: Evidence from China's Loess Plateau

Nuclear factor Y (NF-Y) genes play important roles in many biological processes, such as leaf growth, nitrogen nutrition, and drought resistance. However, the biological functions of these transcription factor family members have not been systematically analyzed in maize. In the present study, a total of 52 ZmNF-Y genes were identified and classified into three groups in the maize genome. An analysis of the evolutionary relationship, gene structure, and conserved motifs of these genes supports the evolutionary conservation of NF-Y family genes in maize. The tissue expression profiles based on RNA-seq data showed that all genes apart from ZmNF-Y16, ZmNF-YC15, and ZmNF-YC17 were expressed in different maize tissues. A weighted correlation network analysis was conducted and a gene co expression network method was used to analyze the transcriptome sequencing results; six core genes responding to drought and rewatering were identified. A real time fluorescence quantitative analysis showed that these six genes responded to high temperature, drought, high salt, and abscisic acid (ABA) treatments, and subsequent restoration to normal levels. ZmNF-YC12 was highly induced by drought and rewatering treatments. The ZmNF-YC12 protein was localized in the nucleus, and the Gal4-LexA/UAS system and a transactivation analysis demonstrated that ZmNF-YC12 in maize (Zea mays L.) is a transcriptional activator that regulates drought resistance and recovery ability. Silencing ZmNF-YC12 reduced net photosynthesis, chlorophyll content, antioxidant (superoxide dismutase, catalase, peroxidase and ascorbate peroxidase) system activation, and soluble protein and proline contents; it increased the malondialdehyde content, the relative water content, and the water loss rate, which weakened drought resistance and the recoverability of maize. These results provide insights into understanding the evolution of ZmNF-Y family genes in maize and their potential roles in genetic improvement. Our work provides a foundation for subsequent functional studies of the NF-Y gene family and provides deep insights into the role of the ZmNF-YC12 regulatory network in controlling drought resistance and the recoverability of maize.

Karst areas are characterized by poor surface water storage capacity, which makes them more sensitive to drought events. To enhance drought resistance in karst landform areas, this study focuses on a typical region in the Yun–Gui Plateau of China, specifically Guizhou Province, which includes 88 counties and districts. According to the regional characteristics, the index system for the assessment of drought resistance and disaster reduction ability was constructed to include 17 indexes in five evaluation layers, including natural conditions, water conservancy project, economic strength, water usage and water conservation level, and emergency support capacity. A comprehensive evaluation was conducted using a fuzzy evaluation model. Furthermore, the drought resistance and disaster reduction capacity of Guizhou Province was evaluated according to the fulfillment of water supply and water demand under the frequency of 75%, 90%, 95%, 97%, and 99% drought frequency inflow in each research unit. This assessment serves to define the spatial distribution pattern of drought resistance and disaster reduction capability within the province. Additionally, according to the results of the supply–demand balance method, the weight of the main influencing factors in regards to drought resistance and disaster reduction ability was optimized and adjusted to identify the key restricting factors of drought resistance and disaster reduction ability. This research data was obtained from the National Disaster Survey database, aiming to provide practical guidance for drought resistance in Guizhou Province. The research findings show that: (1) the distribution characteristics of drought resistance and disaster reduction capability in Guizhou Province are the most significant in Guiyang City, Liupanshui City, and Anshun City in the southwest, with higher drought resistance and disaster reduction ability found in central region, and lower drought resistance primarily identified in the eastern part of Qiandongnan Prefecture, Tongren City, the southern part of Qiannan Prefecture, and the northwestern part of Bijie City; (2) there are six main influencing factors in the three criterion layers, i.e., hydraulic engineering, emergency drought resistance, and social economy, and their contribution rates are as follows: surface water supply and storage rate > average number of soil moisture monitoring stations > per capita GDP > agricultural emergency drought irrigation rate > regional water supply assurance rate > cultivated land effective irrigation rate.

Drought stress is severely damaging during seedling stage of rice (Oryza sativa L.), which can lead to significant yield reductions. Dongxiang common wild rice (Oryza rufipogon Griff., hereafter referred to as DXWR), with strong drought resistance, could be a favorable genetic resource to improve the drought resistance of cultivated rice. Xieqingzao B (O. sativa L. ssp. indica, hereafter referred to as XB) is a representative maintainer line in hybrid rice breeding system in China. By using DXWR as donor parent, XB as recurrent parent, through continuous selfing, backcrossing and strict drought-resistant screening, we developed a strong and stable drought-resistant introgression line IL395 (BC5F10), whose ability of drought resistance was significantly increased than that of the recurrent parent XB at the seedling stage. Meanwhile, no significant differences existed among other major agronomic traits under normal condition, except for plant height. Physiological assessment revealed that IL395 exhibited a significant increase in levels of free proline and soluble sugars, which was associated with drought resistance. Whole genome marker analyses identified genomic segments of DXWR linking with RM171 and RM590 (chr. 10) and RM235 (chr. 12) that require further analysis as possible sources of drought resistance trait. These results suggest that DXWR could be a favorable genetic resource to improve the drought resistance of cultivated rice, and the IL395 might be a useful resource for excavating the drought-resistant genes from DXWR.

速生树种尾巨桉和竹柳因其水分消耗和利用问题引起了一些争议，因而受到了广泛的关注，由于尚缺乏科学的观测数据，而其中许多指责或支持也尚无定论，因此必须深入研究此2种树种耗水性能和水分利用效率，以期科学评价其水分消耗和利用性能。采用盆栽苗木称重法和Li-6400光合系统测定方法分别测定尾巨桉（<em>Eucalyptus urophylla</em>× <em>Eucalyptus</em> <em>grandis</em>）和竹柳（<em>Salix </em>sp.）苗木在不同土壤水分条件下耗水量、耗水速率和苗木不同生长期叶片净光合速率（<em>Pn</em>）、蒸腾速率（<em>Tr</em>）和水分利用效率（WUE），研究表明：（1）正常水分条件下，尾巨桉和竹柳日总耗水量和最大耗水速率分别为（182.05±12.74）g/d、（100.48±10.95）g/d和（66.31±9.91）g·m^-2·h^-1、（89.50±13.54）g·m^-2·h^-1，土壤水分条件下降时，2种苗木耗水量和耗水速率均呈显著下降趋势，严重干旱胁迫时尾巨桉降幅更大。（2）正常水分条件和轻度水分胁迫下2种苗木耗水速率日变化趋势均为明显单峰曲线，且峰值均出现在12：00-14：00，中度干旱胁迫时则其变化趋势呈“双峰”曲线，峰值分别在10：00-12：00和14：00-16：00出现，严重干旱胁迫时日变化规律不明显。（3）正常水分条件和轻度水分胁迫下2种苗木耗水速率与环境温度显著正相关，与相对湿度显著负相关，随着干旱胁迫的发展，环境因子对耗水速率的影响有所减弱。（4）叶片水平来看，与尾巨桉相比，竹柳具有高光合、低蒸腾、高水分利用效率的特点，2种苗木由生长初期进入生长旺期时，净光合速率和蒸腾速率均发生相同幅度增加，而水分利用效率基本保持不变。（5）从单株耗水量和耗水速率以及叶片水分利用效率综合来看，竹柳属节水性能较好速生树种，而尾巨桉虽然存在叶片水平高蒸腾和低水分利用效率的情况，但从单株苗木水平上来讲，其耗水速率甚至低于竹柳，特别在土壤水分严重亏缺情况下其白天平均耗水速率仅为（4.02±0.60）g·m^-2·h^-1，也表现出了一定的抗旱节水能力。;<em>Eucalyptus urophylla</em> × <em>Eucalyptus grandis</em> and bamboo-willow have attracted wide concerns due to the debates on their water consumption (WC) and utilization efficiency problems. Insufficiency of scientific observation data and consequent uncertainty of the rationality of blame or support on the two trees' development make it a necessity to further study their WC characteristics and water use efficiency (WUE). In this study, WC and water consumption rate (WCR) of<em> E. urophylla</em> × <em>E. grandis</em> and bamboo-willow seedlings under different soil moisture conditions were measured by pot seedling weight method, and net photosynthetic rate (<em>Pn</em>), transpiration rate (<em>Tr</em>) and WUE of them in different growth periods were investigated by Li-6400 photosynthetic system measuring method. Under normal water condition, day-and-night WC and maximum WCR of <em>E. urophylla</em> × <em>E. grandis</em> and bamboo-willow seedlings were(182.05±12.74)g/d,(100.48±10.95)g/d, (66.31±9.91)g·m^-2·h^-1 and(89.50±13.54)g·m^-2·h^-1, respectively. Water consumption and WCR of the seedlings significantly declined with soil moisture decreases, with those of <em>E. urophylla</em> × <em>E. grandis</em> declining more sharply than bamboo-willow under serious drought stress. The daily variation of WCR exhibited a one-peak curve (the peak appearing at 12:00-14:00) under normal water condition and light drought stress, but changed to a double-peak curve (the peaks appearing at 10:00-12:00 and 14:00-16:00, respectively)under moderate drought stress, and showed no regular pattern under serious drought stress. Under normal water condition and light drought stress, a significant positive correlation and a significant negative correlation were observed between WCR and environmental temperature and between WCR and relative humidity, respectively. The influence of environmental factors on WCR weakened along with the development of drought stress. At leaf level, bamboo-willow had higher photosynthetic rate and WUE, and lower transpiration rate than <em>E. urophylla</em> × <em>E. grandis.</em> In initial through vigorous growth period, net photosynthetic rate and transpiration rate of both seedlings increased at similar amplitude, while their WUE remained unchanged. In terms of WC and WCR of individual seedling and leaf WUE, bamboo-willow was a good water-saving fast-growing tree species. <em>E. urophylla</em> × <em>E. grandis</em> had higher leaf transpiration rate and lower WUE at leaf level, but had lower WCR at individual seedling level than bamboo-willow, which was particularly true when under serious drought stress, with its average daytime WCR being only (4.02±0.60) g·m^-2·h^-1. Therefore, <em>E. urophylla</em> × <em>E. grandis</em> seedlings also showed a certain ability of drought resistance and water-saving.

In this study, many indexes correlated with drought resistance including yield components, chlorophyll content, the content of proline, the content of malondiadehyde (MDA), the activity of superoxide dismatase (SOD), the content of peroxides (POD) and catalase (CAT) activity soluble protein content and leaf area in flag leaves were measured under water stress after flowering in five rice backcross combinations. The indexes for drought resistance were screened by the correlation and the gray relationship analysis, under water stress after flowering. The results indicated that after flowering, rate of seeds fertilization was significantly correlated with yield remarkably. And proline content, MDA content in flag leaf and leaf areas were significantly influenced with drought resistance in rice, which indicated that it is feasible to predict the drought resistance in rice after flowering. According to the gray relationship analysis, ability of drought resistance in five rice backcross combinations is the following, the combination 5 > combination 1 > combination 4 > combination 3 > combination 2. Results were generally consistent with the performance in field, which indicated that it is reasonable to predict the drought resistance in rice after flowering with the four indexes screened out in this study.

近年来，云南遭受了百年不遇的严重旱灾，林业工程造林正面临着艰巨的考验，培育优良的抗旱树种及探索其抗旱机制显得尤为重要。因此，通过水分梯度法控水，我们从生长指标和生理生化指标等方面研究两种不同繁殖方式的膏桐(扦插苗与实生苗)的抗旱性，并利用SPSS软件进行方差分析和相关性分析、应用隶属函数法对其抗旱能力作出综合评价及比较。结果表明：1) 在不同程度干旱胁迫下，两种不同繁殖方式的膏桐苗木成活率均达到了100%，在重度干旱胁迫的中后期和末期部分叶片才出现了萎蔫、叶片卷曲、枯萎、落叶等现象；2) 膏桐实生苗和扦插苗的苗高生长均受到抑制，且随着干旱胁迫程度的加剧、时间的延长，苗高生长量受抑程度增加；3) 植株总干重、茎干重、叶干重和根干重均呈现下降趋势，与对照相比，膏桐实生苗上述指标的降幅均低于膏桐扦插苗；4) 与对照相比，膏桐实生苗及扦插苗苗木的根冠比都随着干旱胁迫强度的加强和胁迫时间的延长而呈现出明显的上升趋势；5) 苗木叶片相对含水量下降，下降幅度与干旱胁迫强度及时间成正比，且繁殖方式不同，下降幅度不同。由此可知：无论哪种繁殖方式的膏桐在干旱胁迫条件下苗木仍能维持较正常的生理过程，保持相对高的生长速率，抗旱能力较强。根据各项生长指标来判断，膏桐实生苗的抗旱生长略高于膏桐扦插苗。 In recent years, Yunnan had suffered from the worst drought in a century, and there was the big-gest challenge in front of the development of forestry industry, whereupon it would be particularly important for us to cultivate improved drought-resistant species and research its drought resistance mechanism. Therefore the drought resistance of two different modes of reproduction (seedlings and cuttings) of Jatropha curcas was researched from the growth indexes, physiological and biochemical indexes with the moisture gradient method to control water. And then the comprehensive evaluation and comparison of their drought resistance ability was made by use of variance analysis, correlation analysis and application method of subordinate function in SPSS software. The results showed that : 1) under the different degree of drought stress, the survival rate of those two different modes of reproduction seedlings were both up to 100%, and most of leaves didn’t appear wilting, leaf curl, fallen leaves at the middle, late and last phase until under the severe drought stress; 2) the growth in seedling height was restrained with the increase of drought stress degree and the extension of time; 3) the total dry weight of the plant, stem, leaves and root were all in downtrend, compared to check samples, the decline range of above indexes of cuttings of Jatropha curcas was lower than its seedlings; 4) compared to check samples, the root shoot ratio of those two different seedlings took on apparent uptrend along with the increase of drought stress degree and extension of time; 5) the relative water content of seedling leaves declined, and the decline range was in proportion to the degree of drought stress and the length of time. And those two modes of reproduction differed in the decline range. It can be seen that Jatropha curcas seedling in whatever kind of reproduction still could maintain its normal physiological process, maintain relatively high growth rate and drought resistance ability. According to the drought coefficient and the relative growth in seedling height, the drought-resistant growth of cuttings was a little higher than that of seedlings.

Climate-growth pattern of Pinus tabulaeformis plantations and their resilience to drought events in the Loess Plateau

With the continuous drought stress treatment to five Hydrangea macrophylla varieties of different abilities of drought resistance, twenty-five physiological-biochemical indices were mea-sured. We evaluated the drought resistance of different varieties and established the mathematic model. The results showed that leaf mass per area, cell membrane permeability (CMP), the content of malonaldehyde (MDA), the activity of superoxide dismutase (SOD), soluble sugar content, proline content, intercellular carbon dioxide and non-photochemical quenching coefficient were significantly increased under drought stress for twenty days. In contrast, relative water content, net photosynthetic rate, stomatal conductance, transpiration rate, actual photochemical efficiency of PS2 and electron transport rate (ETR) were significantly decreased. The principal component analysis classified those indices into three independent comprehensive indices (accumulative contribution of 87.1%). The principal component 1 mainly reflected the information of photosynthetic and fluorescence. The principal component 2 mainly reflected the information of plant vigor. The principal component 3 mainly reflected the information of membrane system and osmotic adjust system. Five H. macrophylla varieties were divided into three categories by clustering analysis: drought-tolerant type (including H. macrophylla 'Lavblaa') and H. macrophylla 'Taube'), intermediate type (H. macrophylla 'You and me romance'), and drought-intolerant type (including H. macrophylla cv. Endless summer bride and H. macrophylla 'Tricolor'). Comprehensive evaluation of drought resis-tance (D value) showed that the ability of drought resistance decreased in order of H. macrophylla 'Lavblaa' > H. macrophylla 'Taube'> H. macrophylla 'You and me romance'> H. macrophylla cv. Endless summer bride > H. macrophylla 'Tricolor'. Four influential indices for drought resis-tance including CMP, the activity of peroxidase (POD), soluble protein contents (SP) and ETR was screened by stepwise regression analysis, which could be used for the rapid identification of drought resistance of H. macrophylla.

Alleviating effect of extremely low frequency pulsed electric field on drought damage of maize seedling roots

Drought severely affects the growth and development of maize, but there is a certain degree of compensation effect after rewatering. This study intends to elaborate the response mechanism of maize at the physiological and molecular level as well as excavating potential genes with strong drought resistance and recovery ability. Physiological indexes analysis demonstrated that stomata conductance, transpiration rate, photosynthesis rate, antioxidant enzymes, and proline levels in maize were significantly altered in response to drought for 60 and 96h and rewatering for 3days. At 60h, 96h, and R3d, we detected 3095, 1941, and 5966 differentially expressed genes (DEGs) and 221, 226, and 215 differentially expressed miRNAs. Weighted correlation network analysis (WGCNA) showed that DEGs responded to maize drought and rewatering through participating in photosynthesis, proline metabolism, ABA signaling, and oxidative stress. Joint analysis of DEGs, miRNA, and target genes showed that zma-miR529, miR5072, zma-miR167e, zma-miR167f, zma-miR167j, miR397, and miR6214 were involved to regulate SBPs, MYBs, ARFs, laccases, and antioxidant enzymes, respectively. Hundreds of differentially expressed DNA methylation-related 24-nt siRNA clusters overlap with DEGs, indicating that DNA methylation is involved in responses under drought stress. These results provide new insights into the molecular mechanisms of drought tolerance, and may identify new targets for breeding drought-tolerant maize lines.

Arachis hypogaea abscisic acid transporter like-1 (AhATL1) modulates abscisic acid (ABA) sensitivity by specifically influencing the importing of ABA into cells, and is a key player in plant stress responses. However, there is limited information on ABA transporters in crops. In this study, we found that the level of AhATL1 expression and AhATL1 distribution increased more rapidly in the second drought (D2) compared with in the first drought (D1). Compared with the first recovery (R1), the AhATL1 expression level and ABA content remained at a higher level during the second recovery (R2). The heterologous overexpression of AhATL1 in Arabidopsis changed the expression pattern of certain memory genes and changed the post response gene type into the memory gene type. Regarding the proline and water content of Col (Arabidopsis thaliana L. Heynh., Col-0), atabcg22, and AhATL1-OX during drought training, the second drought (D2) was more severe than the first drought (D1), which was more conducive to maintaining the cell osmotic balance and resisting drought. In summary, drought stress memory resulted in a rapid increase in the AhATL1 expression and AhATL1 distribution level, and then raised the endogenous ABA content and changed the post response gene type into the memory gene type, which enhanced the drought resistance and recovery ability.

Drought resistance and recovery ability are two important requisites for plant adaptation to drought environments. Proline (Pro) metabolism has been a major concern in plant drought tolerance. However, roles of Pro metabolism in plant recovery ability from severe drought stress are largely unexplored. Periploca sepium Bunge has gained increasing attention for its adaptation to dry environments. Here, we investigated Pro metabolism in different tissues of P. sepium seedlings in the course of drought stress and recovery. We found that leaf Pro metabolism response during post-drought recovery was dependant on drought severity. Pro biosynthesis was down-regulated during recovery from -0.4 MPa but increased continually and notably during recovery from -1.0 MPa. Significant correlation between Pro concentration and Δ1-pyrroline-5-carboxylate synthetase activity indicates that Glutamate pathway is the predominant synthesis route during both drought and re-watering periods. Ornithine δ-aminotransferase activity was up-regulated significantly only during recovery from −1.0 MPa, suggesting positive contribution of ornithine pathway to improving plant recovery capacity from severe drought. In addition to up-regulation of biosynthesis, Pro transport from stems and roots also contributed to high Pro accumulation in leaves and new buds during recovery from −1.0 MPa, as indicated by the combined analysis of Pro concentration and its biosynthesis in stems, roots and new buds. Except its known roles as energy, carbon and nitrogen sources for plant rapid recovery, significant positive correlation between Pro concentration and total antioxidant activity indicates that Pro accumulation can also promote plant damage repair ability by up-regulating antioxidant activity during recovery from severe drought stress.

BackgroundGlycinebetaine, whose biosynthesis could be catalyzed by choline oxidase (COD), is an extremely efficient compatible solute for scavenging oxidative stress-inducing molecules and protecting the photosynthetic system in plants. To study the effects of the codA transgene for choline oxidase on the drought resistance and recovery, a transgenic potato cultivar (SC) bearing codA gene and a non-transgenic (NT) control cultivar were raised in pots under moderate and severe drought stress. The experiment was constituted by a two-day-pretreatment with 20% PEG and a four-day-water stress combined with two-day-recovery treatment.ResultsUnder the four-day-water stress, plants were provided with normal water condition, 10% or 20% polyethylene glycol. The results of pretreatment showed an expression of codA gene in transgenic potato and an accumulation of glycine betaine (GB); leaf water potential was higher in SC than in NT. In the stress-recovery-treatment, SC showed stronger antioxidant ability, more efficient photosynthetic system, higher chlorophyll content, lower malondialdehyde content and better recovery from water deficit stress than NT.ConclusionAlthough this work concentrated on the short-term water stress and recover treatments on transgenic potato plants with the over-expression of CodA gene and its control line. The datas shows that the exogenous codA gene provided potato a stronger drought resistance and recovery ability.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-54-30) contains supplementary material, which is available to authorized users.