Abstract
Deficiencies in essential mineral nutrients such as nitrogen (N), phosphorus (P), and iron (Fe) severely limit plant growth and crop yield. It has been discovered that both the local sensing system in roots and shoot-to-root systemic signaling via the phloem are involved in the regulation of the adaptive alterations in roots, in response to mineral deficiency. mRNAs are one group of molecules with systemic signaling functions in response to intrinsic and environmental cues; however, the importance of shoot-to-root mobile mRNAs stimulated by low mineral levels is not fully understood. In this study, we established a Nicotiana benthamiana/tomato heterograft system to identify shoot-to-root mobile mRNAs that are produced in response to low N, P or Fe. Multiple long-distance mobile mRNAs were identified to be associated with low mineral levels and a few of them may play important roles in hormonal metabolism and root architecture alteration. A comparison of the mobile mRNAs from our study with those identified from previous studies showed that very few transcripts are conserved among different species.
Highlights
Deficiencies in essential mineral nutrients such as nitrogen (N), phosphorus (P), and iron (Fe) severely limit plant growth and crop yield
We used the heterograft to identify the mRNAs that move from the shoot-to-root in response to low N, P, or Fe after 24 h of mineral deficiency treatment (Figure 1B)
Most prior efforts were focused on local signaling in the roots, but recent evidence has shown that shoot-to-root systemic signaling via the phloem plays an important regulatory role in maintaining mineral homeostasis
Summary
Deficiencies in essential mineral nutrients such as nitrogen (N), phosphorus (P), and iron (Fe) severely limit plant growth and crop yield. Under conditions of N or P deficiency conditions, the root system undergoes a range of adaptive responses, including altered growth on both primary and lateral roots, increased proliferation of root hairs, accelerated exudation of organic acids, and enhanced expression of N or P transporters [1,2,3]. Similar physiological alterations occur when plants experience Fe deficiency in which the growth of lateral roots and the expression levels of Fe transporters in roots are increased. Shoot defoliation or split root experiments, in which roots are divided between mineral-sufficient and -deficient media, showed that the shoot-to-root systemic signaling via the phloem is involved in regulating the adaptive alterations in the roots of multiple species in response to N, P, or Fe deficiency [4,5,6,7,8]. Further analyses have identified multiple mobile components in the phloem that play
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