Aptamers are nucleic acid sequences that specifically bind with target molecules and are vital to applications such as biosensing, drug development, disease diagnostics, etc. The traditional selection procedure of aptamers is based on the Systematic Evolution of Ligands by an Exponential Enrichment (SELEX) process, which relies on repeating cycles of screening and amplification. With the rapid development of aptamer applications, RNA and XNA aptamers draw more attention than before. But their selection is troublesome due to the necessary reverse transcription and transcription process (RNA) or low efficiency and accuracy of enzymes for amplification (XNA). In light of this, we review the recent advances in aptamer selection methods and give an outlook on future development in a non-SELEX approach, which simplifies the procedure and reduces the experimental costs. We first provide an overview of the traditional SELEX methods mostly designed for screening DNA aptamers to introduce the common tools and methods. Then a section on the current screening methods for RNA and XNA is prepared to demonstrate the efforts put into screening these aptamers and the current difficulties. We further predict that the future trend of aptamer selection lies in non-SELEX methods that do not require nucleic acid amplification. We divide non-SELEX methods into an immobilized format and non-immobilized format and discuss how high-resolution partitioning methods could facilitate the further improvement of selection efficiency and accuracy.

As nucleic acid testing is playing a vital role in increasingly many research fields, the need for rapid on-site testing methods is also increasing. The test procedure often consists of three steps: Sample preparation, amplification, and detection. This review covers recent advances in on-chip methods for each of these three steps and explains the principles underlying related methods. The sample preparation process is further divided into cell lysis and nucleic acid purification, and methods for the integration of these two steps on a single chip are discussed. Under amplification, on-chip studies based on PCR and isothermal amplification are covered. Three isothermal amplification methods reported to have good resistance to PCR inhibitors are selected for discussion due to their potential for use in direct amplification. Chip designs and novel strategies employed to achieve rapid extraction/amplification with satisfactory efficiency are discussed. Four detection methods providing rapid responses (fluorescent, optical, and electrochemical detection methods, plus lateral flow assay) are evaluated for their potential in rapid on-site detection. In the final section, we discuss strategies to improve the speed of the entire procedure and to integrate all three steps onto a single chip; we also comment on recent advances, and on obstacles to reducing the cost of chip manufacture and achieving mass production. We conclude that future trends will focus on effective nucleic acid extraction via combined methods and direct amplification via isothermal methods.

Under soil drought conditions, plant roots sense stress and transmit signals to the shoots, leading to coordinated whole‐plant responses to the stress. While several root‐to‐shoot signals have been identified, the existence and significance of shoot‐to‐root signals in this process remain unclear. Here, we identify a two‐step, CLE peptide‐mediated root‐shoot‐root signaling relay underpinning drought adaptation in common bean. We show that PvCLE16 , a gene predominantly expressed in leaves under well‐watered conditions, was specifically upregulated in leaves, but not roots, under moderate drought. This spatially restricted transcriptional activation was driven by the leaf‐preferentially expressed transcription factor PvTCP10. Accumulated PvCLE16 in leaves promoted stomatal closure and also translocated to the roots, where it suppressed primary root elongation and stimulated lateral root development, adaptations that collectively enhance drought resilience. PvBAM3 was identified as the primary receptor for PvCLE16. Upstream of this module, we found that drought‐induced expression of PvCLE16 in leaves requires PvCLE11b, a root‐derived CLE peptide that moved acropetally under drought. Together, our findings reveal a novel root‐shoot‐root signaling relay, wherein root‐derived PvCLE11b functions as the upward signal to induce PvCLE16 in leaves, which subsequently acts both locally and systemically by translocating to the roots to coordinate whole‐plant drought adaptation responses.