High Antioxidant Activity Facilitates Maintenance of Cell Division in Leaves of Drought Tolerant Maize Hybrids.

Viktoriya Avramova,Han Asard,Ivanina Vasileva,Hamada Abdelgawad,Hamada Abdelgawad,Anna Holek,Joachim Mariën,Gerrit T S Beemster,Alexandra S Petrova

doi:10.3389/fpls.2017.00084

Viktoriya Avramova, Han Asard + Show 7 more

Open Access

https://doi.org/10.3389/fpls.2017.00084

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Abstract

We studied the impact of drought on growth regulation in leaves of 13 maize varieties with different drought sensitivity and geographic origins (Western Europe, Egypt, South Africa) and the inbred line B73. Combining kinematic analysis of the maize leaf growth zone with biochemical measurements at a high spatial resolution allowed us to examine the correlation between the regulation of the cellular processes cell division and elongation, and the molecular redox-regulation in response to drought. Moreover, we demonstrated differences in the response of the maize lines to mild and severe levels of water deficit. Kinematic analysis indicated that drought tolerant lines experienced less impact on leaf elongation rate due to a smaller reduction of cell production, which, in turn, was due to a smaller decrease of meristem size and number of cells in the leaf meristem. Clear differences in growth responses between the groups of lines with different geographic origin were observed in response to drought. The difference in drought tolerance between the Egyptian hybrids was significantly larger than between the European and South-African hybrids. Through biochemical analyses, we investigated whether antioxidant activity in the growth zone, contributes to the drought sensitivity differences. We used a hierarchical clustering to visualize the patterns of lipid peroxidation, H2O2 and antioxidant concentrations, and enzyme activities throughout the growth zone, in response to stress. The results showed that the lines with different geographic region used different molecular strategies to cope with the stress, with the Egyptian hybrids responding more at the metabolite level and African and the European hybrids at the enzyme level. However, drought tolerance correlated with both, higher antioxidant levels throughout the growth zone and higher activities of the redox-regulating enzymes CAT, POX, APX, and GR specifically in leaf meristems. These findings provide evidence for a link between antioxidant regulation in the leaf meristem, cell division, and drought tolerance.

Highlights

Drought is one of the most important environmental factors that adversely affects plant growth, reducing yield quality and quantity of economically important crops throughout the world (Boyer, 1982; Tollenaar and Lee, 2002)
We studied the growth of 13 hybrid maize lines with different geographical backgrounds (Western Europe, Egypt, and South Africa) and contrasting drought tolerance, and the reference inbred line B73 under optimal, mild, and severe drought conditions
We add the analysis of 5 Egyptian lines, obtained from an independent breeding program (Sids Research Station, Agricultural Research Centre, Beni-Suef, Egypt) to the kinematic analysis of the African and the European hybrids, and B73, published in our previous study (Avramova et al, 2016) to broaden the genotypic variation and compare the behavior of these groups of lines with different drought tolerance and different origins

Summary

Introduction

Drought is one of the most important environmental factors that adversely affects plant growth, reducing yield quality and quantity of economically important crops throughout the world (Boyer, 1982; Tollenaar and Lee, 2002). Since drought is predicted to become an increasing problem in future climate conditions (Burke et al, 2009; Lobell et al, 2011; IPCC, 2014), an important challenge for plant biologists and breeders is to improve drought tolerance of crops. This is a difficult task due to the diverse strategies adopted by the plants to escape, avoid, or tolerate drought, and the dependence of the response on the timing and severity of the stress and the plant organ affected (Nguyen et al, 2004). We demonstrated that growth of drought tolerant hybrids was less reduced, due to differences in developmental rate, shoot growth rate, photosynthesis, and root system architecture (Avramova et al, 2016)

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