Transcriptomic Changes in Medicago truncatula and Lotus japonicus Root Nodules during Drought Stress.

Izabela Sańko-Sawczenko,Hanna Rekosz-Burlaga,Jakub Mielecki,Barbara Łotocka,Weronika Czarnocka

doi:10.3390/ijms20051204

Izabela Sańko-Sawczenko, Hanna Rekosz-Burlaga + Show 3 more

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https://doi.org/10.3390/ijms20051204

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Abstract

Drought is one of the major environmental factors limiting biomass and seed yield production in agriculture. In this research, we focused on plants from the Fabaceae family, which has a unique ability for the establishment of symbiosis with nitrogen-fixing bacteria, and are relatively susceptible to water limitation. We have presented the changes in nitrogenase activity and global gene expression occurring in Medicago truncatula and Lotus japonicus root nodules during water deficit. Our results proved a decrease in the efficiency of nitrogen fixation, as well as extensive changes in plant and bacterial transcriptomes, shortly after watering cessation. We showed for the first time that not only symbiotic plant components but also Sinorhizobium meliloti and Mesorhizobium loti bacteria residing in the root nodules of M. truncatula and L. japonicus, respectively, adjust their gene expression in response to water shortage. Although our results demonstrated that both M. truncatula and L. japonicus root nodules were susceptible to water deprivation, they indicated significant differences in plant and bacterial response to drought between the tested species, which might be related to the various types of root nodules formed by these species.

Highlights

Plants belonging to the Fabaceae family are unique due to their ability to form symbiotic interactions with nitrogen-fixing bacteria, called rhizobia
In M. truncatula root nodules, an 18% decrease in nitrogenase activity was noted after two days of watering withdrawal, and 66% after four days (Figure 1A)
It has been shown that a drought-related decline in nitrogenase activity is local, rather than systemic in both P. sativum and M. truncatula, since it occurs only in the part of root system exposed to water deprivation [6,26]

Summary

Introduction

Plants belonging to the Fabaceae family are unique due to their ability to form symbiotic interactions with nitrogen-fixing bacteria, called rhizobia. As a result of this interaction, plants receive from bacteria atmospheric dinitrogen reduced into ammonia, which, in contrast to free nitrogen, is suitable for utilisation. Such symbiosis enables fabaceans to reach a high protein content in their tissues, irrespectively of nitrogen soil resource [1]. Taking into consideration the root nodule meristematic activity, there are two types of root nodules—determinate and indeterminate. The symbiosis of M. truncatula with its compatible strain Sinorhizobium meliloti results in the formation of indeterminate nodules [3], whereas L. japonicus develops determinate type root nodules, resulting from symbiosis with Mesorhizobium loti [4]

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