Delayed leaf senescence induces extreme drought tolerance in a flowering plant

Abstract

Drought, the most prominent threat to agricultural production worldwide, accelerates leaf senescence, leading to a decrease in canopy size, loss in photosynthesis and reduced yields. On the basis of the assumption that senescence is a type of cell death program that could be inappropriately activated during drought, we hypothesized that it may be possible to enhance drought tolerance by delaying droughtinduced leaf senescence. We generated transgenic plants expressing an isopentenyltransferase gene driven by a stress-and maturationinduced promoter. Remarkably, the suppression of drought-induced leaf senescence resulted in outstanding drought tolerance as shown by, among other responses, vigorous growth after a long drought period that killed the control plants. The transgenic plants maintained high water contents and retained photosynthetic activity (albeit at a reduced level) during the drought. Moreover, the transgenic plants displayed minimal yield loss when watered with only 30% of the amount of water used under control conditions. The production of drought-tolerant crops able to grow under restricted water regimes without diminution of yield would minimize drought-related losses and ensure food production in water-limited lands.cytokinins ͉ isopentenyltransferase ͉ water stress ͉ water use efficiency ͉ oxidative stress D rought is the most serious environmental factor limiting the productivity of agricultural crops worldwide, with devastating economical and sociological impact. Climate models have indicated that drought episodes will become more frequent because of the long-term effects of global warming (1, 2), emphasizing the urgent need to develop adaptive agricultural strategies for a changing environment. These range from changes in traditional management and agronomic practices to the use of marker-assisted selection for the improvement of drought-related traits and the development of transgenic crops with enhanced tolerance of drought and improved water use efficiency that would minimize drought-related losses and ensure food production for a growing population.Plants can use a combination of different strategies to avoid or tolerate drought stress (3, 4). In arid regions, for example, winter annuals combine a relatively short life cycle with a high growth rate during the wet season to avoid drought altogether. Other types of avoidance include closing of stomata to minimize water loss, adjusting sink/source allocation by increasing root growth, and decreasing canopy by reducing growth and shedding of older leaves (5). Accelerated leaf senescence and leaf abscission are associated with drought in nature as a means to decrease canopy size. In perennial plants, this strategy contributes to the survival of the plant and the completion of the plant life cycle under drought stress. In contrast, this strategy reduces the yields of annual crops, with concomitant economical loss to farmers. We hypothesized that it is possible to enhance the tolerance of plants of drought stress by delaying the drought-induced...

ABA receptor PYL9 promotes drought resistance and leaf senescence

“…ABA-activated SnRK2s then mediate leaf senescence by phosphorylation of Related to ABA-Insensitive 3/VP1 (RAV1) and ABF2 transcription factors, which then up-regulate the expression of ORE1 and other NAC transcription factors, thereby activating expression of SAGs. Previous research has suggested that transgenic plants with delayed leaf senescence are more resistant to drought stress (1). However, we examined the importance of ABA-induced leaf senescence under drought stress and found that the increased leaf senescence in pRD29A::PYL9 transgenic plants apparently helps generate a greater osmotic potential gradient, which causes water to preferentially flow to developing tissues.…”

“…In plants, leaf senescence increases the transfer of nutrients to developing and storage tissues. Recently, studies on transgenic tobacco showed that delayed leaf senescence increases plant resistance to drought stress (1). However, the senescence and abscission of older leaves and subsequent transfer of nutrients are known to increase plant survival under abiotic stresses, including drought, low or high temperatures, and darkness (2,3).…”

The rice transcription factor OsWRKY47 is a positive regulator of the response to water deficit stress

“…They involve regulatory molecules, TFs and hormones such as ABA, cytokinin (CK), ethylene and their crosstalk mechanisms (Peleg and Blumwald 2011). Among these, the CKinduced delayed senescence has been shown to be effective in increasing the tolerance of plants to water deficit (Rivero et al 2007). Transgenic plants expressing the IPT gene, encoding a key enzyme in CK synthesis, under the control of SARK (a stress-and maturity-induced promoter) displayed enhanced photosynthesis and high yields under water stress (Rivero et al 2007;Peleg et al 2011b;Reguera et al 2013).…”

“…Among these, the CKinduced delayed senescence has been shown to be effective in increasing the tolerance of plants to water deficit (Rivero et al 2007). Transgenic plants expressing the IPT gene, encoding a key enzyme in CK synthesis, under the control of SARK (a stress-and maturity-induced promoter) displayed enhanced photosynthesis and high yields under water stress (Rivero et al 2007;Peleg et al 2011b;Reguera et al 2013). A Gene expression profile of flag leaves from wild-type plants and transgenic rice plants expressing P SARK ::IPT, highlighted the differential expression of OsWRKY47 in the P SARK ::IPT plants under water stress (Peleg et al 2011b).…”

Mapping QTL for stay-green and agronomic traits in wheat under diverse water regimes

“…This might be due to fewer known genes and QTL. Until now, the isopentenyl transferase (IPT) gene (Gan and Amasino 1995) has been the most successful application of improving stay-green traits and delayed senescence for increasing productivity in specific crops (Rivero et al 2007;Swartzberg et al 2006), but it does not affect grain yield in wheat (Sykorova et al 2008).…”