Control of Abscisic Acid Catabolism and Abscisic Acid Homeostasis Is Important for Reproductive Stage Stress Tolerance in Cereals1    

Abstract

Drought stress at the reproductive stage causes pollen sterility and grain loss in wheat (Triticum aestivum). Drought stress induces abscisic acid (ABA) biosynthesis genes in anthers and ABA accumulation in spikes of drought-sensitive wheat varieties. In contrast, drought-tolerant wheat accumulates lower ABA levels, which correlates with lower ABA biosynthesis and higher ABA catabolic gene expression (ABA 8#-hydroxylase). Wheat TaABA8#OH1 deletion lines accumulate higher spike ABA levels and are more drought sensitive. ABA treatment of the spike mimics the effect of drought, causing high levels of sterility. ABA treatment represses the anther cell wall invertase gene TaIVR1, and drought-tolerant lines appeared to be more sensitive to the effect of ABA. Drought-induced sterility shows similarity to cold-induced sterility in rice (Oryza sativa). In coldstressed rice, the rate of ABA accumulation was similar in cold-sensitive and cold-tolerant lines during the first 8 h of cold treatment, but in the tolerant line, ABA catabolism reduced ABA levels between 8 and 16 h of cold treatment. The ABA biosynthesis gene encoding 9-cis-epoxycarotenoid dioxygenase in anthers is mainly expressed in parenchyma cells surrounding the vascular bundle of the anther. Transgenic rice lines expressing the wheat TaABA8#OH1 gene under the control of the OsG6B tapetum-specific promoter resulted in reduced anther ABA levels under cold conditions. The transgenic lines showed that anther sink strength (OsINV4) was maintained under cold conditions and that this correlated with improved cold stress tolerance. Our data indicate that ABA and ABA 8#-hydroxylase play an important role in controlling anther ABA homeostasis and reproductive stage abiotic stress tolerance in cereals.

A phenotypic marker for quantifying heat stress impact during microsporogenesis in rice (Oryza sativa L.)

“…The probability of these combined stresses damaging rice crops in the major ricegrowing regions in Southern and South-east Asia has been recently mapped (Wassmann et al 2009). The rice scientific community has intensified efforts to develop rice varieties capable of withstanding these adverse conditions (heat stress, Yoshida et al 1981;Jagadish et al 2010aJagadish et al , 2010bJagadish et al , 2011drought stress, Bernier et al 2007;Kumar et al 2008;Venuprasad et al 2008; cold stress, Andaya and Mackill 2003;Ji et al 2011) to sustain rice production under future adverse climates. Rice is extremely sensitive to these stresses, in particular, during the reproductive -gametogenesis and flowering stages -and exposure can result in increased spikelet sterility, which in turn, reduces grain yield.…”

Potential role of D-myo-inositol-3-phosphate synthase and 14-3-3 genes in the crosstalk between Zea mays and Rhizophagus intraradices under drought stress

“…However, under drought stress, AM plants, considered to be more tolerant to drought (Augé 2001;RuizLozano 2003), accumulated less ABA, as described by Ji et al (2011) (Supplementary Table 3). The suppression of AO was one of the main reasons for lower ABA concentration in mycorrhizal plants (Supplementary Table 4).…”

Yield stability for cereals in a changing climate

“…Spikelets and florets also abort when stresses occur later during floral development (Dolferus et al 2011). The fixation of grain number is, therefore, a dynamic process that is determined continuously by the environment throughout reproductive development.…”

“…However, ABA biosynthesis does also occur in the anthers and ABA can repress sugar transport to pollen by downregulating cell wall invertase expression. Downregulation of anther ABA levels using transgenic approaches resulted in improved stress-tolerance (Ji et al 2011).…”

“…Detailed accounts of the problems generally associated with quantitative trait loci (QTL) mapping for abiotic stress tolerance in cereals have recently been published (Collins et al 2008;Fleury et al 2010;Dolferus et al 2011). Breeding programs tend to focus on commercial factors such as high yield potential and grain quality, not on abiotic stress tolerance.…”